Volume 88, (Quarterly Issue) Part 1.

Issued May, 1960

Published by the Royal Society of New Zealand,

Victoria University of Wellington, P. O. Box 196,

Wellington, New Zealand

Editor: J. T. Salmon, D. Sc., F. R. S. N. Z., F. R. E. S.

Associate Editor:

Sir Charles Cotton, D. Sc., Hon. LL. D., A. O. S. M., F. G. S., F. R. S. N. Z.

London Agent.

High Commissioner for New Zealand, 415 Strand, London, W. C. 2.

Printed by Otago Daily Times and Witness Newspapers Co., Ltd.,
Dunedin, New Zealand.

Ground Water Conditions in Canterbury

By P. J. Alley

Contributions to the Knowledge of the New Zealand Bryophyte Flora

By K W Allison

Natural Acaena Hybrids in the Vicinity of Wellington

By J. W. Dawson

Prince of Wales Park, Brooklyn

This Acaena population was found within the city area in the vicinity of a football ground known as Prince of Wales Park. The excavations made in 1932 to form this field resulted in steep banks, about 30ft high, along the western side. North of the centre line these appear to have slipped, forming a 30–40° slope with dimensions of approximately 60 yards by 15 yards. It was on this comparatively even surface that the Acaena population was found.

The pattern of the population is illustrated in Fig. 3. The plants referred to as Acaena novae-zelandiae or A. anserinifolia were readily identified in the field; the former by their dark-green foliage, shining upper leaf surfaces and large fruiting heads with long, bright crimson spines; the second by their lighter brown-green foliage, dull upper leaf surfaces and small fruiting heads with short brownish spines. Plants forming the extensive colony to the northern end could not be identified, but evidence obtained from progeny tests strongly suggested that they were hybrids between the two species present.

Text-fig. 3.—Population pattern, Prince of Wales Park.

As the date of formation of the habitat is definitely known, the population as a whole could not have been older than 21 years at the time of study. An attempt was made to determine the ages of individual plants by means of ring counts but little significant information was obtained for the following reasons:

(a) The annual rings were only weakly developed;

(b) In all cases the oldest woody parts available had broken ends directed away from the growing point. It is possible, therefore, that the first-formed parts of such branches, if they could be traced, would be several years older than those actually obtained. A maximum of 4 annual rings was found in the 2 species and the hybrids.

In many cases apparently separate plants were found to be in connection with one another over a distance of several yards. It seems, therefore, that individual plants spreading vegetatively by this means could eventually cover a considerable area.

The 18 glasshouse plants were scored for characters a, b, c, d, e, f, g, h, j, J The extreme scores for Acaena novae-zelandiae and A. anserinifolia in this case were 0 and 17 respectively. The progeny of their suspected hybrid scored as follows: 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 9, 9, 9, 10 (Fig. 4.)

The 15 garden plants were scored for characters d, e, f, h, i, j, J. The scores of Acaena novae-zelandiae and A. anserinifolia for these characters are 0 and 8 respectively. The progeny of their suspected hybrid scored as follows: 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 6. (Fig. 4.)

Discussion

A comparison of the forms of Acaena novae-zelandiae and A. anserinifolia in this locality with forms of the two species elsewhere reveals that the first is relatively large and the second relatively small in most measurable characters. The contrast between the two species is therefore particularly marked in this locality.

The hybrid hypothesis advanced in explanation of the unidentifiable colony was based on the following evidence.

(1) The plants possessed a mixture of the distinctive features of the two species present.

(2) Germination rates and pollen fertility were both low.

(3) Progeny obtained showed marked segregation for all characters.

Text-fig. 6.—Lyall Bay-Seatoun. First leaves from 10 plants of the suspected hybrid progeny.

The supplementary hypothesis that the field hybrids were all F₁ plants is based on the following evidence:

(1) The field hybrids appeared to be uniform and intermediate between the two species present.

(2) The average pollen fertility of the field plants is 32.25% and that of their progeny 75.3% Such an improvement in fertility has been observed by other workers in the F₂ generation of interspecific hybrids.

The extent of the suspected hybrid colony appears to contradict this hypothesis, for if the increase in area has been due to the production of new plants, then there should be a significant proportion of F₂ plants in the colony. However, the spreading and rooting habit of the Acaenas, which is an effective means of vegetative reproduction, suggests that the colony may have been entirely derived from a few original F₁ plants.

The low germination rate of seed from these presumed F₁'s and the low survival rate of seedlings suggests that F₂ plants would find difficulty in establishing themselves under field conditions.

In Fig. 4 it will be noted that the average hybrid index is displaced towards Acaena novae-zelandiae. A. possible explanation is that in the case of three characters scored in the more than two grades A. novae-zelandiae is probably overrepresented— ie, with growth habit inherent lack of vigour may reduce the number and length of laterals formed, and with cotyledon-length and first-leaf form, in respect of which the majority of seedlings resembled Acaena novae-zelandiae, A. novae-zelandiae dominance is probably a factor. The approximately normal curve formed by the hybrid indices does not suggest backcrossing to Acaena novaezelandiae.

Lyall Bay-Seatoun Coast

This area is a strip of coastline approximately three miles long partly within and partly outside the entrance to Wellington Harbour. It consists for the most part of a narrow coastal platform (averaging about 25 Yards wide) backed by steep hills. The platform came into being partly as a result of general uplift during the 1855 earthquake and the habitats so formed were later considerably modified by the construction of a coastal road in 1923. The soil consists mainly of rock fragments mixed with shingle and a small amount of sand.

An extensive area of sand dunes formerly existed at Lyall Bay, but these were later levelled to make way for housing and for Rongotai aerodrome. A comparatively sandy area also exists at the head of Tapiri Bay, and a few sand dunes still remain along the Seatoun foreshore.

The coastal platform supports a rather stunted grass cover with scattered prostrate shrubs, and a similar association is found on the lower hill slopes. On the latter, however, growth is generally more vigorous and in places where there is a certain amount of seepage, almost luxuriant. The major part of the area would be fully exposed to southerly gales.

The population pattern of Acaenas in this area (Fig. 5) is not nearly so straightforward as at Prince of Wales Park. The most common type, indicated by the letter H. on the map, could not be assigned to any known species. The type marked P? was at first identified as Acaena novae-zelandiae var. pallida but later comparisons showed it to be smaller than the common type of that species in all respects. The type marked P. was indentified as Acaena novae-zelandiae var. pallida. Specimens in various herbaria indicate that this variety was also quite common on the formerly existing sand dunes at Lyall Bay.

Only one plant of Acaena novae-zelandiae (marked N) and four plants of A. anserinifolia (marked A) were found and these were at some distance from the unidentified populations.

Ring counts were not attempted in this area, but many plants had quite thick woody parts at the base which resembled those collected at Prince of Wales Park.

Seeds were collected from three Hand one P? colony, from one plant of Acaena novae-zelandiae var. pallida, from one plant of A. novae-zelandiae and from two plants of A. anserinifolia.

The plants of Acaena anserinifolia and A. novae-zelandiae differed in minor details only from the forms at Prince of Wales Park.

• (e) Fruit spines pale-red and partly colourless — field hybrids. Characters which suggest Acaena anserinifolia as the other parent involved are:

• (a) Leaf, stem and fruit spine dimensions of the field hybrids are generally less than those of the Acaena novae-zelandiae and more or less intermediate between those of A. novae-zelandiae var. pallida and A. anserinifolia. (See table.)

• (b) Simple first leaves — 3 plants (progeny).

• (c) Stems pale-brown — 2 plants (progeny).

• (d) Distinct red-brown colouration on the upper margins of leaflets — 3 plants (progeny), also field hybrids.

• (e) Extensive purple colouration on the under surfaces of leaflets — 2 plants (progeny), also field hybrids.

• (f) Fascicled hairs at the serration tips — 1 plant (progeny).

• (g) Some degree of hairiness on the upper surfaces of leaflets — 8 plants (progeny) also field hybrids.

The evidence derived from stem, leaf and fruit spine dimensions can be demonstrated most effectively in tabulated form. Averages for the three local species were based on collections from several localities in the study area.

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The evidence suggesting Aceana novae-zelandiae var. pallida and A. anserinifolia as the parent species of the hybrid colonies is therefore fairly strong.

The question arises—where did the hybrids originate and how did they become established at such widely separate points? The comparative rarity of possible parents in the vicinity makes speculation difficult. Two possibilities are:

(1) That crossing has taken place outside the area (possibly at Lyall Bay when Acaena novae-zelandiae var. pallida was common there) and hybrid seeds have been carried into the coastal section at various times by people and animals.

(2) That isolated plants of Acaena novae-zelandiae var. pallida have established themselves in sandy spots along the coastal section from time to time and have produced hybrid seed as a result of fertilisation by windborne pollen of distant A. anserinifolia. The inconspicuous flowers, prominent plumose stigmas and elongate stamens of the Acaenas suggest wind rather than insect pollination.

Both suggestions presuppose a selective influence of the environment which discourages establishment of Acaena novae-zelandiae var. pallida seedlings and encourages the hybrids. The majority of habitats available along the coastal strip are certainly unsuitable for Acaena novae-zelandiae var. pallida.

Wainui Valley and South Karori Stream

Plants which are undoubtedly hybrids were discovered at the above localities, and in both cases Acaena anserinifolia and A. novae-zelandiae were observed in the vicinity. The hybrids were not subjected to detailed study but sufficient information was obtained to suggest that they were first generation crosses between the above two species.

Hybrid seed from the South Karori Stream had a germination rate of 38% reduced to an effective rate of 36% by the death of one seedling.

The first leaves varied in form from simple to trifoliate. Simple — 4 plants; simple, deeply incised—3 plants; trifoliate—11 plants. Adult leaves varied greatly in size, shape and colour.

In the Wainui-o-Mata Valley seed was collected from two plants suspected to be hybrids between Acaena anserinifolia and A. novae-zelandiae in the vicinity. The first had a germination rate of 40% reduced to an effective rate of 16% by the death of several seedlings. The first leaves were as follows: simple — 3 plants; simple deep incised—3 plants; trifoliate—5 plants.

The second seed lot had a germination rate of 14%, reducing to an effective rate of 12%. The first leaves were as follows: simple—3 plants; simple deeply incised—3 plants; trifoliate—6 plants.

Southern Tararuas and Kapiti Island

The Acaenas in these localities belong almost exclusively to one species — Acaena anserinifolia. Acaena novae-zelandiae was observed at only one locality in the southern Tararuas. The form of Acaena anserinifolia on Kapiti Island is similar to those in the Wellington area, but the commonest form in the Tararuas was distinctive in the following respects: relatively large leaves and incised leaflets; distinct pilosity of the upper surfaces of all leaflets; and a preference for the semi-shady habitats of bush tracks.

The few plants of Acaena novae-zelandiae mentioned above were found at widely separated points near the bank of the Tauwharenikau River. In each case a few plants were found in the vicinity which were possibly interspecific hybrids between Acaena novae-zelandiae and the common Tararua form of A. anserinifolia. These possible hybrids had the dark-green foliage, red stems and crimson spines of Acaena novae-zelandiae, but their general dimensions were less and there was a noticeable degree of pilosity on the upper surfaces of their leaflets.

Colour Variation in Acaena anserinifolia

The majority of plants of Acaena anserinifolia observed had red and purple pigments in addition to chlorophyll. At a number of localities there were a few uniformly bright-green plants which lacked the secondary pigments. These plants bred true for this character Some of the plants possessing secondary pigments bred true, but in others a proportion of the offspring had secondary pigments, while in a lesser proportion these pigments were lacking. Figures for the latter phenomenon in the various localities were as follows:—

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The overall ratio of progeny with secondary pigments to progeny lacking secondary pigments is 2.7: 1. It seems, therefore, that the production of secondary pigments is controlled by a single genetic factor whose recessive allele is inhibiting when homogygous.

These occasinal plants lacking secondary pigments are probably the form described by Cockayne as Acaena anserinifolia var. viridior (Cockayne, 1916).

General Discussion

As a result of the present study it is concluded that the production of F₁ hybrids by the three local species of Acaena is quite frequent in the Wellington area. These hybrids are considered to be of two types: (1) Crosses between Acaena novaezelandiae var. pallida and A. anserinifolia (Lyall Bay-Seatoun); (2) Crosses between Acaena novae-zelandiae and A. anserinifolia (Prince of Wales Park, South Karon Stream, Wainui Valley and possibly in the Tauwharenikau Valley).

With the second type of cross a few plants of Acaena novae-zelandiae were generally found in association with the suspected hybrids. This suggests that Acaena anserinifolia normally acts as the male parent and this is probably explained by the following facts. The generally early flowering habit of Acaena anserinifolia combined with the pronounced proterogyny of all species means that when the first stigmas are appearing on the flower heads of the later flowering species only Acaena anserinifolia pollen is available. In all probability the majority of hybrids are produced in this way, and it follows that Acaena anserinifolia is most frequently the male parent.

The question aries whether the incidence of natural hybridism has always been so high or whether it is largely a recent phenomenon coinciding with the period of Europeans settlement in New Zealand. The latter view is favoured by the author, for, since European settlement, the distribution pattern of the lowland Acaenas must have been greatly altered, and as a result opportunities for hybridism must have increased immeasurably.

A comparison of pre- and post-European times with respect to conditions of dispersal and the extent of available habitats should make this clear.

In pre-Europeans times the only agents for achene dispersal were the Maori and his dog and possibly some of the flightless birds. There are no antive land mammals in New Zealand and the Maori had no form of animal husbandry. In these times, too, the country was largely covered with forest, so open habitats suitable for Acaena were much less common than now. With white settlement came the introduction of domesticated animals, notably sheep, and other animals which became established in the wild—deer, pigs and rabbits. In time the lowland areas were cleared of forest and brought into cultivation, and since that time the creation of disturbed habitats by roading and other construction works has been a recurring phenomenon. Thus, settlement has caused a marked increase in the number of dispersal agents and a parallel increase in the total area of habitats suitable for Acaena.^*. The result has been an overlapping of the three species throughout their ranges, and a consequent increase in the opportunities for hybridism.

Studies in Pimelea I—The Breeding System

By C. J. Burrows, Botany Department, University of Canterbury.

basis, Lewis and Crowe (1956) have re-examined the field in terms of orthodox genetics since then. Some of the data published by Correns is found, in the light of work by East (1934, ex Lewis 1956), to be explicable on an orthodox genetic basis. C. & H. Yampolsky (1922) list only 97 species of 5 genera as being gynodioecious. They mention Pimelea as having 70–80 species, hermaphrodite polygamous or dioecious. Baker (1948) gave more than 70 species in 16 families in which functional female flowers were smaller than functional hermaphrodites. Many of these were gynodioecious. The Thymelaeaceae (to which Pimelea belongs) was not listed by him. Godley (1955 and 1957) described gynodioecy in Fuchsia, Cyathodes and Leucopogon in New Zealand.

Gynodioecy in Pimelea

In the most careful description of polymorphism in Pimelea flowers yet published, Thomson (1880) concluded that P. prostrata, “Though hermaphrodite in structure… is dioecious in function and will probaly tend rapidly to become so in structure as well”. Thomson described hermaphrodite forms where the style lengthened after the flowers opened until it extended beyond the anthers. Other dioecious forms had large male flowers on some individuals and smaller females on others. In the former, the short style, with tiny stigma, lengthened and protruded between the lobes of the flower tube, although the ovary then shrivelled. The female plants had flowers with a long style, a large capitate stigma and aborted anthers. P. longifolia was described by the same writer (Thomson, 1927) as being polygamous and dioecious.

Cheeseman (1925) gives as a generic character for Pimelea that the flowers are hermaphrodite but functionally dioecious or occasionally polygamo-dioecious and that “The male flowers are the most numerous….” Cheeseman designates as polygamo-dioecious³, erroneously, some 10 of the species described by him in the “Manual” including P. traversii and P. prostrata. The other species he describes are not classified, as to breeding system. Cheeseman (1914), figured four species and gave similar details. Parlane (1925) wrote about floral features in Pimelea but followed Cheeseman.

Dr. E. Godley (pers. comm.) has found that P. longifolia and P. virgata are gynodioecious. He has noted that in the specimens used by Cheeseman for the illustrations of P. longifolia (sheets 5336.1 and 5336.2 in the Cheesemand herbarium) all hermaphrodites have protruding styles so that the male flowers described by Cheeseman are not present. It seems probale that Cheeseman had observed hermaphrodite flowers in different stages of development.

As well as for the four species at Cass, the present writer has observed that P. aridula, P. sericeo-villosa, P. pseudo-lyalii and P. arenaria have female and hermaphrodite flowers on separate plants. It will be shown that on functional grounds also the Cass Pimeleas are gynodioecious.

Australian and Tasmanian writers, Black (1952) and Cruickshank (1953) have not used the term gynodioecy for the type of breeding system in Australian Pimelea spp. The former says of the genus, that species are “bisexual or unisexual by abortion of stamens or ovary, often diocious”. The latter describes some species as dioecious. It appears that there is greater variation in types of breeding system in Australia than in New Zealand. Descriptions of some of the large number of Australian species of Pimelea (Bentham, 1873) leave little doubt, however, that gyno-

dioecy is present Species with large hermaphrodite flowers and small females on separate plants exist, but other species described appeared to be wholly hermaphrodit.

Flower Structure

The flower of Thymelaeaceous plants is considered by Heinig (1951) to be an expanded torus, with the calyx at the end of the floral tube. The flower is best referred to as the flower tube, and this term will be used in future discussion of Pimelea flowers.

A description of the flowers of one of the Pimelea species at Cass, in general terms, will cover all of them, except in gross dimensions, since little other difference is to be seen in flowers from different species.

Flowers are terminal and grow erect in dense heads of 10–20 flowers. They are almost sessile on very short stalks, and at the base of the flowers is a dense growth of silky hair which remains after the fruit has fallen. The flower tube is cylindrical, with four calyx lobes at the distal end of a hollow tubular torus. The lobes are small and spreading when the flowers are open. Petals are absent, but the torus is petaloid. The upper side of the calyx lobes and inside of the floral tube is waxy white and usually glabrous (some hairs may be found, especially in P. traversii, inside the tube) and bears very small tubercles which give a shining appearance. The outer wall of the flower tube and underside of the calyx lobes are densely clothed with simple hairs. The base of the tube, surrounding the ovary, is red in P. prostrata, P. “snow tussock” and P. “short tussock” Especially in female flowers this area is often folded, and bulging. The hermaphrodite flower tube base bulges less and is narrower and longer than in females. The hermaphrodite flower tube base bulges less and is narrower and longer than in females. The flowers of P. prostrata, P. “short tussock” and P. “snow tussock” have a distinctly sweet scent, but the scent of P. traversii is negligible Nectar is produced in both females and hermaphrodites, apparently by morphologically unspecialised cells on the inner walls of the flower tube. It lies here, about half way up the tube or at the bottom of the tube.

Measurements of the long axis of flower tubes in from 20–30 plants (average of 5 flowers per plant) in both sexes of each species at Cass are given below.

In all cases the hermaphrodite flower tubes are larger than the female ones, although in any one species, a few individuals of either sex approach one another in size. Other structural differences between hermaphrodite and female are also

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In P. “snow tussock”, P. “short tussock” and P. prostrata only the base is left, but in P. traversii the whole hairy flower tube is left surrounding the ovary, although not adherent to it.

The fruits of P. “snow tussock” and P. “short tussock” are oval, yellow, orange, or red and fleshy. They are somewhat flattened laterally, and the seed, black, hard and oval, is imbedded in the fleshy portion. Fruits of P. prostrata are similar in size, but snow white and fleshy. In these plants fruits are produced in large numbers in crowded clusters. Very few of the flowers of females do not produce fruit. In P. traversii there is a small green, hard fruit. Fruits are quickly shed when ripe from all four species.

Natural Populations

The table above shows the numbers of different sexes of plants counted in line transects at Cass in the season, summer 1957–58. The counts were made of every flowering plant on lines through each population. The ratios of the sexes one to another are also given. Included in the table also are figures for counts along the same transects at different parts of the flowering season and for some counts made of plants at Erewhon, in the Rangitata watershed in 1957, at the Macaulay River, and at Lake Tekapo in 1959. The plants counted at different parts of the flowering season will, in most cases, be different individuals, since any one plant flowers for a comparatively short period.

The above figures should be compared with figures for absolute numbers of fruit set and for percentage fruit set in the same species at Cass. The latter were arrived at by counting between 20–30 flowers in heads of individual plants, then marking these and finally counting the number of fruit set for each of these. For 20 plants (10 of each sex) about 25 flowers each were counted in an area of a few square.

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The importance of these tables in showing that, firstly, the different Pimelea spp. vary considerably with respect to proportions of different sexes in the populations and secondly, population differences in the same species from area to area indicate that breeding system structure varies from population to population. The figures given by Godley (1955) for variation in proportion of females to hermaphrodites in Fuchsia from area to area show similar conditions. The differences from species to species are probably inherent in the genetics of the plants, but the population differences may be due to selective influences. An examination of these figures shows that at Cass both P. “snow tussock” and P. “short tussock” with 50% each of females and hermaphrodites in the population also have about 20 female to 1 hermaphrodite fruit set. This is important as a compensating factor, allowing the high proportion of females to be maintained in the field. On the other hand P. prostrata and P. traversii, with only about 30% of female plants in the population, have about 10 female to 1 hermaphrodite and 2 female to 1 hermaphrodite fruit set respectively. The higher proportion of hermaphrodite fruit set determines that fewer females may be retained in the population. It is to be expected that the Erewhon population of P. prostrata has yet a lower female fruit set. Low fruit set in hermaphrodites may perhaps be connected with incompatibility. Although these figures are indicative, and most useful in gauging the nature and extent of gynodioecy in Pimelea spp., the picture would be more complete with a study of the proportions of female to hermaphrodite seed which viable. This was not carried out owing to lack of time and difficulty of germinating seed.

The differences in fruit set compared with percentage numbers of the different sexes in the field in P. prostrata and P. traversii indicate differences in the sex determination mechanisms. It will be noticed that the percentage of female flowered plants counted in the populations of P. prostrata and P. traversii early in their flowering seasons was greater than at a later stage. There may be some connection in this with hormone balance. The higher proportion of female flowers open early in the season could, however, if insect vectors are active, contribute to the high proportion of females in the population. The competition between insects for flowers might have some bearing on this.

Crossing Experiments

Some closely controlled experiments were carried out at Christchurch and at Cass, where plants of the four different species were used to assess relative amounts of fruit set by female and hermaphrodite plants upon artifical crossing. Selfing of hermophrodites and cross pollination of hermaphrodites and females were used in these intraspecific crosses. No adequate figures for statistical treatment were obtained and no seed could be germinated to test viability. All flower heads used were bagged prior to opening of flowers, and care was taken to avoid accidental crosses. In all cases females set fruit in a high percentage of flowers, but very few attempts at crossing and selfing of hermaphrodites were successful. Enough evidence was gathered to show that P. “snow tussock”, P. “short tussock” and P. prostrata (the two latter more rarely) can all set fruit through self pollination of hermaphrodite flowers, but it is obvious that this is less efficacious than cross pollination of females. Cross pollination of emasculated hermaphrodites also results in a low percentage of fruit set in P. “snow tussock”.. Upon selfing, only a few fruit per head were set at Christchurch on P. “snow tussock” hermaphrodites but P. traversii hermaphrodites at Cass showed higher self fertility (8–10%). Artificial crosses with hermaphrodites thus resulted in fruit set comparable with that in natural conditions. Dr. E. Godley (pers comm.) has verified self fertility of hermaphrodites for P. traversii.

These experiments in Pimelea show that, in fact, not much more than half the amount of genic material supplied to a new generation comes from the hermaphrodites in P. “short tussock” and P. “snow tussock”, since hermaphrodite fruit set, whether due to selfing, or cross fertilization, is very low in them. Hermaphrodite fruit set is only about 4–5% of the total fruit set by females in natural populations of these two taxa. In P. prostrata the percentage fruit set of hermaphrodites as compared with females is also low—about 10%, but in P. traversii it is much higher —just less than 50%. The systems of inheritance of sex may differ between P. traversii and the other species but it is possible for them all to have a genetic basis. Cruickshank (1953) discussing Tasmanian species of Pimelea stated that “All species examined have fertile pollen, and there is no evidence of any apomixis in the genus.” The specimens from Cass were tested for apomixis by bagging (and emasculation of hermaphrodites) but no fruit was set by unpollinated flowers. All the species had apparently fertile pollen. Examination was made of pollen stained with cotton blue in lactophenol, and in each species the grains were full. Only a small percentage of pollen was deformed, abnormally small or empty.

The Pollen Vectors

Numbers of insects were captured on flowers of the various species of Pimeleas at Cass Some were sent to the Cawthron Institute for identification, and Dr. E. S. Gourlay determined some of these. Other insects were determined by Dr. R. Pilgrim of the Zoology Department, University of Canterbury. The writer made further determinations by comparison of insects with already identified specimens. The details about insects are tabulated below.

Most of the flies, the little purple butterfly, Crysophanus boldenarum and the small bee Halictus huttonii are ubiquitous in the short tussock areas at Cass. On fine days when Pimeleas are flowering, some flies and the bee in particular are present in large numbers, flying from flower to flower. Their main purpose is to suck nectar, and pollination is achieved incidentally to this, except in the case of occasional pollen collection by Halictus. Close observation showed that flies and bees had pollen adhering to body hair and on the head. Occasional individuals of Halictus collected pollen on the hind tibia. Although pollen was seen on bees and flies none of this was examined closely. The foraging range of individual insect species was also not examined closely but some general observations were made. Of the more frequent visitors, most of the Dipterans seemed fairly restricted in range. Crysophanus boldenarum, however, although it remained in one area for a time, was able to fly long distances. Halictus huttonii has its home in clay patches and banks, and is a solitary bee, but is quick flying and appeared to be the most widespread pollinating agent. Halictus and some of the flies by virtue of their presence in numbers are the most important vectors. Hundreds of bees and flies are found within areas of a few hundred square yards. Up to a dozen bees could be seen on one plant or small group of plants and half a dozen flies would be present in the same area. The insects moved quickly from flower to flower. Nectar, which accumulates at or near the bottom of the floral tubes was eagerly sought. Scent is most noticeable on sunny days about the plants (except P. traversii) and combined with the white shining calyx lobes serves as a daytime attractant to butterflies, bees and flies.

Apart from sweet scent and colour the showiness of flower heads is important. Although individual flowers are small, their presence in crowded heads with up to 1,000 flowers per plant ensures that a showy mass of flowers is presented to insect visitors. The flower heads of P. traversii are extremely showy.

In visiting Pimelea flowers there was no distinction by the insects between female or hermaphrodite plants growing side by side. Several plants of P. “snow tussock”, P. “short tussock” and hybrids (between them) were seen to be visited.

indiscriminately by the same bee or fly. At this time, the same vectors were observed visiting P. prostrata plants. Few insects were seen on any one P. traversii plant. While it was noticed that flies and Halictus worked systematically over a flower head in the othe species, in P. traversii, Crysophanus sallustius was seen to be present for long periods and is an important vector.

Most P. traversii individuals flower later than the other Cass species, and most of the individuals grow amongst thick scrub, so that this may account for different animal populations on P. traversii. However, a number of single plants of P. traversii are mixed with all the other species in some areas and flowering times overlap. Similarly P. prostrata, P. “snow tussock” and P. “short tussock” are all juxtaposed in some places and these all have overlapping flowering times. In any one day the P. “snow tussock” plants, growing in shady places, are visited for shorter times by the sun-loving flies, butterflies and bees than are P. prostrata and P. “short tussock” in open sunlight. Some P. “snow tussock” plants grow on fans and exposed places, however.

No night flying insects have been taken into account in describing pollinating agents, but many moths are found in the tussock country. The scented white flowers of P. prostrata, P. “short tussock” and P. “snow tussock” no doubt attract night flying insects. Since distances between different Pimelea species, flowering at the same time, are not great in some places at Cass (some are only feet apart), the physical possibility of cross pollination between species as well as outbreeding within species is important in considering hybridization and variation. The non-selectiveness of unspecialized vectors may help to account not only for similarity in flowers in different Pimelea species but for the amount of hybridization taking place. (See Thomson, 1880, 1927). A. number of the same insects have, in fact, been captured on as widely different genera as Aciphylla, Leptospermum, Leucopogon, Brachycome, Celmisia and Hypochaeris, but when Pimeleas were in full flower other profuse flowerers like Leptospermum were not yet out. It was not ascertained whether one individual Halictus restricted itself to one genus or not.

The effect of heavy rainfall on pollination and fruit set is difficult to gauge. In the 1957-58 summer it appeared to have had considerable significance in decrease of total fruit set. The flowers of one head may be opening over a period of a little more than a week, and the flowers of each plant over a two-week period. They soon wither and die when fruit begins to form or if they are unpollinated. Most plants of any one taxon in a given area flower together. If some catastrophe occurs this may result in a reduction in numbers of fruit set. As a general observation, it was noticed that much more fruit were set, especially in P. “short tussock” and hybrids in the summer of 1956–57. P. traversii and P. prostrata were less affected. Heavy continuous rain affects not only the ability of insects to fly and seek nectar, but it may drown out such ground dwellers as Halictus and also fills floral tubes with water, washing pollen off anthers. The most favourable weather for animal activity and for optimum attractiveness to animals of Pimelea flowers is the hot, dry, sunny weather usually experienced at flowering time.

Relations of Floral Parts at Pollination

Growth of floral parts is important when detail of the breeding system is to be considered. In both females and hermaphrodites it was noticed that after flower opening, the styles elongated and were conspicuously exserted. At first, this was thought to indicate that hermophrodites were protandrous, since anthers dehisced as soon as flowers were open. However, Dr. E. Godley (pers. comm.) noticed that only in unpollinated flowers were styles strongly exserted. A series of tests, consisting of bagging, emasculating (hermaphrodites) and pollinating flowers, showed that this was so. From the time of flower opening both female and hermaphrodite.

It is a possibility that some pollination is brought about by wind in Pimelea, but pollen is heavy and shedding of pollen from inward facing anthers, unless it is carried away by insects, usually results in the bottom of the hermaphrodite flower tube being filled with pollen grains. Since the receptive stigma is below the level of the anthers, although usually to one side of the floral tube, there is a strong chance of pollen falling on it. This does not often occur or the resulting pollination is not effective, as is shown by the large number of exserted styles seen in the field in hermaphrodites. It has been shown previously that effective pollination inhibits style growth in both female and hermaphrodite flowers. In the field, fertilized flowers with non exserted styles were seen to bear pollen on their stigmas and occasionally pollen could be seen on exserted styles.

Modifications of Sex Expression

Some plants in cultivation, and others in the wild populations at Cass and Macaulay River were noticed to bear female flowers in the same heads as hermaphrodites. These do not conform strictly to the implications of the term gynodioecy but are gynomonoecious. At Christchurch P. “snow tussock” and P. prostrata plants, members of clones, bore mixed flowers, although in each case the rest of the clone was made up of purely hermaphrodite plants. At Cass a few plants of all the species had the same condition, but P. traversii always had more female flowers on hermaphrodite plants than the others. The numbers of female flowers could have had some effect on the genetic structure of the species in P. traversii (since fruit set was established for female flowers in mixed heads) but probably is not important for the other species. In several cases, P. traversii plants marked as females early in the season, with hundreds of female flowers, had, later in the season, hundreds of hermaphrodite flowers. Many other plants had numbers of female flowers in hermaphrodite heads. Production of a few female flowers en bloc at the beginning of flowering by an otherwise hermaphrodite plant was the most usual situation. The early production of female flowers on these plants—they are usually the outermost flowers and first to open, suggests difference in environmental treatment. The differences must, however, be slight in nature. Heslop-Harrison (1957) puts the cause of such phenomena in flowering plants to variations in hormone supply.

Checks of the numbers of different sexes of P. “short tussock” and P. “snow tussock” at Cass in both 1956–57 and 1957–58 summers revealed that there was no change in relative numbers of sexes from year to year. It seems that, although immediate control of sex may be hormonal, the ultimate causes of sex difference are genetic.

In addition to production of clearly female and hermaphrodite flowers in the same head, some of the Christchurch and Cass plants were noticed to have “intersexed” flowers. Most of the female flowers on hermaphrodite plants had typical female dimensions. A few such flowers had one anther and small stigma papillae, but female dimensions. Others were larger than females, although smaller than hermaphrodites and some had large and some small papillae. Further female plants with a few flowers having one or two anthers were seen. A very few plants in a population were hermaphrodites with very small flowers or very large flowered hermaphrodites. Again this tends to bear out the idea that sex is controlled, immediately, by a hormonal balance mechanism.

Sex Determination

The determination of sex in Pimelea is of some interest. It is highly probable that size of flower and other polymorphic variations are linked to the cause of sex difference. Some meagre data about time of differentiation of female flowers show that pollen is produced but degenerates in the anthers of at least some flowers.

Chromosome counts of stages of meiosis could be made from anthers of some female flowers of P. traversii and, especially in a few flowers of P. “short tussock” and P. “snow tussock”, pollen was noticed during the very early development of female buds in marked plants. By the time buds were ready to open their anthers were shrivelled and pollen was unrecognizable. In one female P. “short tussock” plant with mature flowers, the anthers, indehiscent and shrivelled, contained collapsed pollen. Frankel (1940) found this phenomenon in Hebe townsoni. Some of the meiotic figures in plants at Cass (the sexes of the parent plants were not determined) appeared to show one set of unpaired chromosomes during second metaphase. These may have been females with degeneration setting in. In Pimelea some emasculated hermaphrodite flowers showed slight reduction in size from normal.

It appears possible that corolla growth is influenced by a hormone produced in the anthers and released post-meiotically. Determination of corolla lengths probably occurs at a stage later than that of the determination of sex of the flower. A paper by Plack (1957) deals with a very similar situation in a sexually dimorphic Labiate, Glechoma hederacea. In this normally gynodioecious species she found that some individuals produce female flowers only, others are gynomonoecious, and the proportion of female to hermaphrodite flowers varies with the stock and the season. This parallels the situation in P. traversii at Cass in all respects. Glechoma is four anthered. Flowers intermediate in size between the small females and larger hermaphrodites had one, two or three anthers. Artificial emasculation of hermaphrodites in bud showed that corolla size was reduced. Plack thought that corolla growth is influenced by a hormone produced in the anthers and released after meiosis since the critical time for growth of corolla (or lack of it) was at a certain corolla length. There appears to be a close similarity between Pimelea and Glechoma in these respects.

In a more recent paper (Plack, 1958) it is shown that treatment with Gibberellin caused growth of small female corollas in Glechoma, to the larger hermaphrodite size.

Baker (1948) states that the wide range of dicotyledons in which small female flowers and larger hermaphrodites are found indicates a common factor in their origin, and there is a strong suggestion from the above evidence that hormone balance controls flower size. A considerable body of information is summarized by Heslop Harrison (1957) who wrote of experimental modification of sex expression. It has been shown in certain plants that various factors of environment may affect development of flowers (with consistent experimental results for either monoecious, dioecious or hermaphrodite plants) causing variations in sex expression. These variations are considered to be due to hormonal causes, the environmental factors affecting production or movement of hormones which control sex. Heslop Harrison suggests that, as flowers are initiated at the apices, the auxin levels favouring optimum development of one sex suppress the other. In a normal environment the mechanism of sex inheritance establishes in some individuals one developmental path and in some the other.

Baker (1948) states that “Because functional pistillate flowers may be distributed in a gynodioecious or gynomonoecious manner in the same species, abortion of anthers cannot always be determined by direct genetic means…”. These ideas do not, however, necessarily conflict with the concept of genetically controlled gynodioecy. Most individuals in populations of Pimelea are clearly of one sex or the other and remain so from year to year.

Discussion

The Pimelea species at Cass, and others in New Zealand are gynodioecious both in structure and function, although some variations in sex expression are extant, as they are in many plant and animal populations. Some genetic experiment is needed to establish the basis for control of sex determination in Pimelea and to discover reasons for variation between different populations in numbers of the sexes. In wild populations the presence of relative proportions of one sex to another is interpreted by Heslop-Harrison (1957) as being due to the interaction of environment with the hormone system of the plants. In Pimelea maintenance of a high proportion of females benefits the species by ensuring outcrossing. This is enabled by activity of animal pollinating agents and the dimorphism of the sexes. Differences in pollinating species in different areas may contribute to variations in proportions of females to hermaphrodites. Ford (1957) in discussion of “intersexes” and the heterostyly of Primula shows how the control of these conditions is genetic and changes are induced by selective influences.

Gynodioecy is in the main an outbreeding system. The higher the proportion of females to hermaphrodites, the greater the amount of outcrossing which is possible. Thus P. “short tussock” and P. “snow tussock” each with 50% of their populations females, at Cass, potentially are able to exchange genes most readily within or between species. The consequences of this, especially with regard to the plasticity of and hybridization between the Pimelea species are most interesting. The probable selective action of flower structure and insect activity in maintaining this situation are supplemented by the low fruit set in hermaphrodite plants as compared with females. However, a little inbreeding can take place, and this could also be of benefit. In P. prostrata and P. traversii the proportion of females is not as high but must also have an important bearing on their variation and ability to hybridize. It is clear, however, that the amount of hybridization between them and other species is more limited than between P. “snow tussock” and other species. They are also less variable throughout their range than P. “snow tussock”. The outbreeding of the latter thus contributes to its plasticity and to the amount of hybridization occurring between it and other species, including P. aridula and P. sericeo-villosa at Cass and elsewhere. Some of this hybridization (observed in terms of variations in morphology and supported by experimental work) is very far-reaching, and probably of the type described by Anderson (1953) and others, as introgression. Widespread hybridization in the genus Pimelea may be attributed in a large measure to gynodioecy in many of the species.

Acknowledgments

The writer is indebted to Professor W. R. Philipson for much assistance and encouragement and to Dr. E. Godley for his most valuable advice and criticism. The information which he made available was extremely helpful. Many other people assisted in various ways and their help is gratefully acknowledged.

References

Anderson, E., 1953. Introgressive Hybridization. Biol. Revs., 28, p. 280.

Baker, H. G., 1948. Corolla Size in Gynodioecious and Gynomonoecious Species of Flowering Plants, Part II. Proc. Leeds Phil. Lit. Soc., 5, p. 136.

Bentham, G. and von Mueller, F., 1873. Flora Australiensis, London.

Black, J. M., 1952. The Flora of South Australia, Part III. p. 592.

Burrows, C. J., 1958. Variation in Some Species of the Genus Pimelea. M.Sc. Thesis, University of Canterbury Library.

The Subalpine Scrub of the Hokitika Catchment, Westland

By P Wardle

I. Classification of the Communities

In the following account, the subalpine scrub vegetation is subdivided into categories, each named according to the most abundant dominant species. The following categories are recognised:

• Hoheria glabrata low forest.

• Olearia low forest.

• Olearia colensoi scrub.

• Dracophyllum uniflorum scrub.

• Dacrydium biforme scrub.

• Cliff communities.

Under each heading, there is a description of a typical community, followed by a general account. All the typical communities were described in the top basin of the Toaroha River, while the general accounts have been compiled from observations made throughout the Hokitika catchment.

Hoheria Glabrata Low Forest

Typical Community

Altitude, 3,200ft. Slope, 38°. Aspect, N. E.

Canopy. Pure Hoheria, the trees being 15–20ft tall, with diameters averaging 10in. ^* Stand apparently even-aged.

Ground Cover. Dense Polystichum vestitum. Ranunculus hirtus is the main plant between the clumps of fern. Coprosma depressa and Astelia cockaynei are less common.

Regeneration. Hoheria seedlings up to 3 years old and 6in tall are abundant. Apparent saplings of Hoheria are really coppice shoots from stumps of decadent trees. Saplings of Olearia ilicifolia 1–10ft tall are frequent.

Soil 1in: Matrix medium-dark brown, fine sand, with numerous small schist fragments; loose crumb structure.

2in: Grey zone, probably slightly leached.

>5in: Light brown sand and stones.

The material of the whole profile is loose. Roots are distributed throughout but are densest at 0–1in. Earthworms are present.

General Account

Hoheria glabrata communities are always found on young, deep, moist, welldrained soils, the usual habitats being healed slips, talus slopes and alluvial fans. Due to the rapid erosion, these habitats are extensive, and Hoheria forest comprises a large proportion—perhaps a third—of the vegetation of the scrub belt. The main features are the dominance of Hoheria in the canopy and of Polystichum vestitum in the ground cover. Olearia ilicifolia is usually present, and may be co-dominant. Species less constantly present include Olearia lacunosa, Coprosma ciliata and Phormium colensoi.

Below 2,500–2,800ft the numerous small trees which colonise similar habitats at low altitudes begin to enter; the first are Fuchsia excorticata and Aristotelia serrata. A. community of Hypolepis millefolium, Polystichum vestitum, Danthonia flavescens and Phormium colensoi often develops on young, loose soils both above the altitudinal limits of Hoheria, and in places where the succession to Hoheria forest is delayed.

The pH values of several samples of soil collected in July, 1959, were measured with a Marconi pH meter (Type TF 889/1), using a mixture of approximately 2 volumes of water to 1 of soil. Two samples of soil collected under Hoheria forest at depths of 1–3 inches gave values of 5.1 and 5.3.

(C.f. Hoheria glabrata low forest, Cockayne, 1928, p. 267.)

Olearia Low Forest

Typical Community. Altitude, 2,800ft. Slope, 5°. Aspect, N. E.

Canopy. Co-dominance of Olearia lacunosa, Dracophyllum traversii and Hoheria glabrata. There is also some Olearia ilicifolia. The Dracophyllum traversu is 20–25ft tall and about 10in in diameter. The lower parts of the trunks are inclined downhill; in some trees the trunks are prostrate for a length of 6ft, but no adventitious roots were detected Olearia lacunosa is as tall, and grows to 20in in diameter Hoheria glabrata is a smaller tree.

Shrub Storey. Open, includes Coprosma ciliata and C. pseudocuneata.

Ground Cover This is sparse, due to browsing and trampling. Polystichum vestitum, Coprosma depressa and Uncinia sp are the most important species. There are also Phormium colensoi and Astelia cockaynei.

Regeneration. Seedlings of Olearia ilicifolia and O. lacunosa are common (being comparatively browse-tolerant or unpalatable). There are occasional young plants of Dracophyllum traversii.

Soil. There is a continuous litter of Dracophyllum traversu leaves.

4in: Fine sand, coloured dark brown by humus.

8in: Grey-brown silty sand with numerous, unweathered fragments of schist Roots are mostly between the surface and 6in depth.

General Account

Communities such as the above occupy, like the Hoheria glabrata low forest, deep, moist, freely drained soils But the soils are older with more advanced development of profile, and the communities are more varied and richer. On the old alluvialfan where the typical community is sited, there is considerable variation. Dracophyllum traversu, Olearia lacunosa, O. ilicifolia and Hoheria glabrata may each be clearly dominant, or conversely, absent over small areas. The shrub storey shows similar variations Usually the canopy of Olearia low forest is pierced by trees of Libocedrus bidwillii and occasionally by Podocarpus hallii Olearia colensoi, Senecio elaeagnifolius and Archeria traversii are present where the tree canopy is not continuous.

Olearia Colensoi Scrub.

Typical Community. Altitude, 3,200ft Slope, 45°. Aspect, N. E.

General Shrub Canopy. Olearia colensoi contributes half of the canopy. The plants measure 12ft from ground to apex, but grow nearly horixontally. Archeria traversii, Senecio elaeagnifolius and Olearia lacunosa are also important. There are scattered bushes of Dracophyllum longifolium.

Discontinous Storey of Tallers Shrubs. Dracophyllum traversii forms scattered groups. The stems are up to 10in in diameter and 20ft tall, and their lower parts are inclined.

Ground Cover. Blechnum minus forms a dense sheet, except in the darkest places. Scattered Phormium colensoi and Astelia cockeynei.

Regeneration. No young plants of Dracophyllum traversii, D. longifolium and Archeria traversii were seen. There are occasional seedlings of Senecio elaeagnifolius and Olearia lacunosa. Small seedlings of Olearia colensoi are abundant everywhere, and they succeed in gaps. Occasional small seedlings of Hoheria glabrata do not become established.

Soil. ¼in : Litter.

2in: Dark brown, structureless fine sand.

3in. Medium brown, fine sand, with occasional schist fragments.

>5in: Light brown, fine sand. The proportion of weathering schist particles increases with increasing depth.

General Account

Communities similar to the one described occupy all scrub land sites where the slope is steep, the drainage free, the soil shallow, and the exposure not extreme. They comprise about half of the vegetation of the scrub zone. Their characteristic feature is the dense storey of shrubs, mainly Olearia colensoi, with groups of taller Dracophyllum traversii. Dracophyllum longifolium is usually present, and on drier or warmer sites, such as slight spurs and terrace faces, it may rise to dominance.

On exposed ridges, especially those with northerly aspect, Olearia colensoi scrub passes gradually into communities dominated by Dracophyllum uniflorum. There is a corresponding decrease in height of the scrub, and an increase in the proportions of certain species, notably Dracophyllum longifolium, Olearia lacunosa, Gaultheria rupestris and Coprosma serrulata. On southerly faces low-growing communities of nearly pure Olearia colensoi intervene between tall scrub and grassland.

Occasional slipping of the substratum may explain the occurrence of scattered plants of Hoheria glabrata and Olearia ilicifolia. Gaps often contain herbfield inclusions with Aciphylla (?) colensoi, Celmisia coriacea, Danthonia flavescens (usually the very broad-leaved form), Astelia cockaynet and Phormium colensoi.

In a downhill direction, with the entry of Libocedrus bidwillii, Olearia colensoi scrub passes into high altitude forest. The following pH values were obtained from a soil supporting a community in which Olearia colensoi and Dracophyllum longifolium share dominance:

(C.f. shrub composite scrub of Southern Alps and mountains of north-western district, Cockayne, 1928, p. 278).

Dracophyllum Uniflorum Scrub

Typical Community. Altitude, 3,800ft Slope, 43°. Aspect, N. E. Steep ground on the crest of a ridge.

Shrub Storey. Dense clumps of Dracophyllum uniflorum 2–3 feet tall.

Ground Cover. Mainly Blechnum minus and large moss (genus Dendroligotrichum.) Also Gaultheria sp., Suttonia nummularia, and Schoenus pauciflorus. Occasional clumps of Phormium colensoi, Danthonia flavescens (2 forms), and Celmisia coriacea.

Regeneration. Seedlings of Dracophyllum uniflorum were not seen; but the bushes are propagating by “downhill layering”. One chance seedling of Hoheria glabrata seen.

Soil. ¾in : Black humus.

2in: Dark brown, fine sand.

>5in: Grey-brown, fine sand, containing weathering fragments of schist.

General Features

On exposed ridges, especially those with northerly aspect, Olearia colensoi scrub peters out into Dracophyllum uniflorum communities like the one described. Further, Dracophyllum uniflorum is dominant in the stunted outliers of scrub which occupy rock spurs up to 4,500ft. These high-altitude communities merge into grassland; the shrub component is predominant on steep slopes and shallow soils, the grasses are predominant on gentler slopes and deeper soils (Plate 3, Fig. 2).

(C.f. Dracophyllum scrub: Cockayne, 1928, p. 280.)

Dacrydium Biforme Scrub

Typical Community. Altitude, 2,800ft. Slope, 23°. Aspect, N.E.

Discontinuous Storey of Stunted Trees. Scattered Dacrydium biforme up to 12ft tall, with distinct erect trunks up to 16m in diameter.

Main Shrub Storey. 3–5ft tall, consisting of dense clumps with spaces between. Main species are shrub-form Dacrydium biforme, Dracophyllum longifolium, Olearia colensoi and Archeria traversii. Other species are Nothopanax lineare, N. simplex, Pittosporum divaricatum, Coprosma pseudocuneata and C. colensoi.

Ground Cover and Low Shrubs. The herbs are found mainly between the clumps of bushes, and include Celmisia armstrongii, C. walkeri, Schoenus pauciflorus, Astelia cockeynei, Blechnum minus, Sticherus cunninghamu and Lycopodium scariosum. Danthonia flavescens grows in the widest gaps. Podocarpus nivalis occurs abundantly, and Coprosma serrulata less so, mainly within the shrubby clumps.

Regeneration. No seedlings of Dacrydium biforme were seen, but the bushes propagate freely by downhill layering. All ages of Olearia colensoi and Dracophyllum longifolium are represented.

Soil. ¼in: Humus.

4in: Silty loam, coloured grey by humus. There are a few small schist pebbles. On solid schist, weathering at top.

The upper part of the profile is very wet, and water collected in the pit dug for the examination of the profile. The depth of soil varies; over a fissure in the bedrock it was at least 14m deep, and well drained.

General Account

Dacrydium biforme is conspicuous where the soils are cold and poorly drained. Such conditions occur on gentle slopes where the soil texture is too fine to permit free vertical drainage. On old moraine in the top Toaroha basin, Dacrydium biforme is important on puggy soils, which have developed an alpine gley profile. The following soil description is typical of alpine gley:

Surface flat. Altitude, 2,500ft. The soil forms a matrix between morainic boulders.

¼in: Litter.

4–6in: Greyish brown, fine sand with loose, weak crumb structure. Many roots. Transition to:

3–4in: Bluish-grey, fine sand, puggy and compact, with blocky structure. Weathering pebbles present, and there are also conspicuous reddish-brown blotches which appear to represent the last traces of pebbles destroyed by weathering. Sharp and irregular transition to:

¼in: Reddish-brown, soft iron pan. This gradually lightens in colour to:

2–4in: Light reddish-brown, moderately compact fine sand with weathering pebbles. Gradual transition to:

≥ 4in: Light brown, with a bluish tinge, compact sand. Samples taken from a soil of this type gave the following pH values:

Most of the Dacrydium trees here are growing over morainic boulders which project up to 2 feet above the level of the surrounding ground. They accumulate from several inches to a foot of black raw humus between their roots. A sample of this humus gave a pH value of 4.3.

Where the soil is shallow over solid rock, as in the typical community, the soil water is kept near the surface and conditions again induce Dacrydium biforme scrub. Dacrydium biforme is also common on poorly drained soils in the forest zone, right down to lowland terraces where it is joined by the other Dacrydium spp. characteristic of the “pakihi” habitat.

(C.f. cupressoid-podocarp scrub, Cockayne, 1928, p. 279.)

Cliff Communities.

Under the excessively wet climate of Westland, cliffs cut in moraine and alluvium support dense vegetation. In the scrub zone, the characteristic species are Olearia arborescens, Dracophyllum longifolium, Carmichaelia grandiflora, Coprosma depressa, Phormium colensoi, Danthonia cunninghamii, and Blechnum minus.

II. Autecological Notes on Dominant Species

The following notes summarise the site requirements and features of the regeneration of the most important shrubs. Counts of growth rings form the basis for estimates of growth rate. These counts were made in the field, using a hand lens.

The results were plotted, and estimates of growth rate have been read off. These estimates are merely preliminary approximations; for the slow-growing species, they are gross over-estimates of growth rate, since microscopic examination will certainly reveal more rings than could be detected in the field.

The figures in brackets following the estimates of growth rates are the approximate heights and diameters attainable by mature plants in the scrub zone; but it must be stressed that with all the species discussed, these dimensions vary greatly according to the habitat.

1. Hoheria glabrata is dominant on recent fans, slips and talus slopes between 2,500ft and 3,500ft, but the species ranges from 1,500ft to 4,000ft. Chance seedlings occur nearly down to sea level. Newly germinated seedlings appear in profusion near parent trees, but they do not often survive the attacks of deer. J. T. Holloway (pers. com.) has noted vivipary during wet years, but it is not known whether the seedlings can become established.

The tree is deciduous, and in the summer of 1957–58 the leaves did not expand until December. I have not ascertained the time of leaf-fall, but the total growing season cannot exceed four months. Despite this, H. glabrata is one of the fastest growing subalpine shrubs and trees, as the following estimates show :

Height growth, 1.5in per year (25ft). Growth rings per inch, 36 (24in).

2. Olearia colensoi is the most abundant shrub of the scrub zone, and it occurs in all communities except Hoheria glabrata forest and the higher and more exposed Dracophyllum uniflorum scrub. On steep southerly faces low clumps of O. colensoi

communities which occupy less rigorous habitats, and from dense Danthonia flavescens grassland.

D. uniflorum has the strongest development of the downhill layering habit. Especially on slopes of over 30°, the branches on the downhill side become procumbent, produce adventitious roots, and eventually become separated from the parent plant. With continual layering of the downhill branches, and death of the older uphill shoots, the whole colony migrates downhill.

Estimates of growth rate:

Height growth, 0.4in per year (5ft).

Growth rings per inch, 110 (2in).

These figures suggest that colonies of D. uniflorum can be extremely old.

8. Dacrydium biforme grows on leached soils with poor drainage. The altitudinal range is sea level to 3,000ft, but in the upper Hokitika catchment there are few suitable habitats below 2,000ft. At its upper limits, D. biforme is always a low shrub with prostrate outer branches, while within the forest zone it is nearly always a tree. In an intermediate belt it occurs both as a shrub and as a tree. Plants of intermediate size and form are rare. The shrubby forms show marked downhill layering.

Estimates of growth rate:

Height growth, 0.5in per year (20ft).

Growth rings per inch, 120 (18in).

Some trees which exceed 18in diameter may prove to be well over 1,000 years old.

III Effect of Fire and Herbivorous Mammals on the Subalpine Scrub

A few small areas of scrub near tracks have been burnt. An area in the middle Toaroha, burnt 10 years ago, is a typical example. On a 35° slope Dracophyllum traversii, Olearia lacunosa and O. colensoi were co-dominant before the fire. Phormium colensoi is now the physiognomic species. Polystichum vestitum and Hypolepis millefolium are also important. There is profuse regeneration of shrubs, now 1–3ft tall. Seedlings examined had 6–7 growth rings. The most abundant seedlings are those of the light demanding Olearia ilicifolia which was probably rare or absent in the original scrub. Seedlings of Olearia colensoi are common. There are also hybrids between Olearia lacunosa and O. ilicifolia. Even where this fire extended onto a 70° slope, there is now dense vegetation dominated by Phormium colensoi.

Red deer and chamois both feed within the scrub zone, and their effects were not distinguished from each other. Though Hoheria glabrata is palatable, there does not appear to be much damage to trees in established Hoheria forest; but isolated Hoheria trees are usually badly damaged or killed through removal of bark by chewing and rubbing, and the animals are almost completely preventing regeneration and the establishment of new Hoheria communities on bared areas. The usual community of young alluvial fans and healing slips is now an open one containing Poa cockayniana, Helichrysum bellidioides, Danthonia cunninghamii and browsed, suckering Carmichaelia grandifolia; on steep slopes Hypolepis millefolium is dominant. These communities are being invaded gradually by shrubs, especially the browse-resistant Olearia ilicifolia.

In the true scrub communities the impenetrability and low palatability of most of the species discourage the deer and chamois. Therefore their activity is mostly confined to the formation of sharply defined tracks on the crests of spurs and ridges, leading from the forest to the grassland. Along these tracks, shrubs die and are not replaced. The tracks tend to enlarge into erosion channels, and such grassland species as Danthonia flavescens and Celmisia spp. enter. Away from the tracks there are surviving plants of highly palatable species, notably Nothopanax colensoi and

N. simplex. Along the margins between scrub and grassland, and in places where shrubs are scattered through grassland, less palatable species—especially Dracophyllum uniflorum— are heavily browsed in the winter.

From the point of view of the control of deer and chamois the scrub belt is important. Its position as a barrier between forest and grassland allows the animals to use the uppermost forest almost undisturbed by hunters, who work either from the valley tracks or from the grassland. This uppermost forest is severely damaged throughout the Hokitika catchment.

Hares are present, and in winter they probably make considerable use of the scrub, but their effects were not recognised.

Mature specimens of Hoheria glabrata, Olearia colensoi, O. lacunosa and O. ilicifolia growing within the forest zone are often badly defoliated and, at least sometimes, opossums are responsible. However, no serious damage to the subalpine scrub was noted, although the animals range throughout. There is an exception to this statement; on fault-shattered terrain above the Kokatahi gorge, areas of scrub have died. Opossums are notoriously thick in the forest below, and probably overpopulation has forced numbers of them into the scrub.

Discussion

1. Factors Determining the Grouping of Scrub Species

The ranges of species in the subalpine scrub are apparently determined by their tolerances in respect to several sets of factors, especially soil depth and drainage, altitude and exposure, and light avaiable to the seedlings. A community is formed by species whose tolerances overlap; the richest communities are included in the Olearia colensoi scrub, where there is most overlap (Tables 1 and 2).

There is a close connection between variations in soil and vegetation. The soils which support Hoheria glabrata forest are immature, deep, moist and well-drained. Olearia forest grows on similar, but older, soils; the richer communities, which include the very slow-growing Dracophyllum traversii among the dominant trees, and the more developed soil profiles reflect the longer occupation. Olearia colensoi scrub and Dracophyllum uniflorum scrub usually grow on sites so sleep that the shallow soils cannot develop more than rudimentary profiles, though occasionally one sees deep, brownish-yellow sub-soils which indicate greater maturity of profile. The poorly-drained soils which support Dacrydium biforme have well-developed leached or gley horisons. The fine puggy texture which impedes the drainage of some of these soils may itself be a result of advanced weathering.

It is most probable that differences in nutrient status among these soils influence the vegetation quite so much as do the physical differences. For example, the favourable physical properties of the soils which support Hoheria glabrata forest are possibly reinforced by a better nutrient status. The possibility receives some slight support from the two measurements of p^H, which were 0.3 and 0.4 units higher than the highest readings from soils supporting other communities.

To a certain extent, altitude and exposure have similar effects on the vegetation. Thus, Dracophyllum uniflorum ascends highest and is also dominant on sharp ridge crests. However, Olearia colensoi is the uppermost shrub on moist southerly faces, perhaps because it can compete with dense Danthonia flavescens.

The light demands of seedlings have important bearing on regeneration and succession. Dracophyllum longifolium and D. uniflorum seedlings demand most light for their establishment, and this is in keeping with the preponderance of these species on spur and ridges. Where there is full light and suitable soil conditions, Hoheria glabrata and Olearia ilicifolia seedlings are the most rapidly growing; thus they are able to occupy their preferred sites to the initial exclusion of other shrubs

An Interpretation of the Senecio lautus Complex in New Zealand

By Robert Ornduff Department of Botany, University of Washington

The results of morphological studies are the main basis for the taxonomic treatment herein, but much useful comparative data have come from field studies, garden cultures, distribution patterns, artificial hybridisations, and chromosome counts. The term species when used here refers to a population system which is internally homogeneous with respect to most of the properties of its members and is separated from other related groups by discontinuities in morphology. These discontinuities have been shown to be the result of some genetic, geographical, and/or ecological barriers to any large-scale gene exchange. The term subspecies refers to two or more regional facies of a species which possess relatively minor distinguishing features; the term variety is not used. The foregoing statements refer to the taxonomic structure, which has seemed to be the most practical and useful method of handling the rather complex pattern of variation exhibited by this group of Senecio species.

Since the four species discussed in this paper have, at one time or another, been considered synonymous, the term “species complex” is used in this historical sense and does not cannote the meaning of a group of closely related species. The treatment of this group of species was evolved as a result of the analysis and integration of a number of lines of evidence. It was necessary to examine all the available herbarium material of members of the complex and of related species, to collect living materail, to observe populations in the field, to review pertinent literature, and to conduct breeding experiments and cytological investigations. Using these methods, it has been possible to construct a reasonably workable taxonomic framework into which the majority of the specimens of the complex fit and which seems to reflect natural relationships more adequately than have the previous taxonomic treatments of the group.

Acknowledgments

It is a pleasure to take this opportunity to thank Professor H. D. Gordon and the faculties of the Botany and Zoology Departments at Victoria University of Wellington for their hospitality during my stay in New Zealand. Special thanks are due the late H. H. Allan, G. T. S. Baylis, T. Carrick Chambers, John W. Dawson, A. P. Druce, N. L. Elder, C. Leo Hitchcock, M. D. King, George Mason, Lucy B. Moore, Mrs. P. R. Woodhouse, Sheila Natusch, Graham Pritchard, Graeme Ramsay, Ross G. Robbins, G. M. Schulze, Margaret Simpson and Colwyn Trevarthen, who have contributed in various ways to the completion of this work. I. would also like to thank the staffs of the herbaria for extending the use of their facilities and making loans during the course of the project. I. am deeply indebted to A. R. Kruckeberg, of the University of Washington, for his valuable advice on many of the problems which arose from time to time. Finally, I. gratefully acknowlege the generous financial support of the United States Educational Foundation in New Zealand.

Key to the Taxa of the Senecio lautus Complex

III. Senecio radiolatus

(2) Leaves usually somewhat fleshy and otherwise not as above (3).

(3) Heads large, the disk 1.5–2 cm in diameter; leaves to 10 cm long, pinnatifid; habitat the nesting grounds of sea-birds on offshore islands.

II. Senecio sterquilinus

(3) Heads smaller, the disk well under 1.3 cm in diameter; leaves merely serrate, but if deeply pinnatifid then under 6.5 cm long and habitat not as above (4).

(4) Plants fleshy and very succulent, low, sparingly branched; the leaves entire or pinnatifid with broad lobes, the leaf margins revolute; internodes shortened and the leaves subopposite or whorled at least below; ray florets recurved, the ligules under 4 mm long.

Ib. Senecio lautus ssp. carnosulus

(4) Plants fleshy, but not succulent; low or erect much-branched plants, the leaves usually pinnatifid at least above, the leaf margins not revolute; ray florets with ligules usually over 4 mm long and not revolute.

Ia. Senecio lautus ssp. lautus

(5) Ligules absent; plants of screen of the North and South Island mountains.

IVd. Senecio glaucophyllus ssp. discoideus

(5) Ligules present; plants of more stable ground (6).

(6) Stems erect, branched from the base but usually simple above; leaves pinnatifid; heads usually borne in corymbs.

IVc. Senecio glaucophyllus ssp. raoulii

(6) Stems erect or decumbent, but leaves not deeply pinnatifid (7)

(7) Stems erect, branched at the base but usually quite simple above; leaves serrate; heads borne in corymbs; plants of higher altitudes in the northern South Island.

IVa. Senecio glaucophyllus ssp. glaucophyllus

(7) Stems erect or decumbent, simple or more often freely branched above; leaves serrate or incised; heads borne loosely; plants of coastal areas in the eastern South Island.

IVb. Senecio glaucophyllus ssp. basinudus
Herbarium Studies

The following herbaria were visited or furnished loans of material of the species in the Senecio lautus complex; abbreviations which are used in the text and specimen citations are those suggested by Lanjouw and Stafleu (1956). The abbreviation marked with an asterisk is not listed by them and is original. Since many New Zealand collectors do not use collection numbers, the citations of representative herbarium specimens which follow the discussion of each taxon are transcriptions from the labels on the specimens. If duplicates are present in other herbaria these transcriptions should facilitate their identification. Specimens cited in the text are not listed again in the sections listing representative specimens.

• Auckland Institute and Museum, Auckland (AK).

• Bernice Bishop Museum, Honolulu (BISH).

• Botany Division, DSIR, Christchurch (CHR).

• Canterbury Museum, Christchurch (CANTY).

• Royal Botanic Gardens, Kew (K).

• British Museum, Natural History (BM).

• National Herbarium of Victoria, South Yarra (MEL).

• Museum of Natural History, Paris (P).

Systematic Treatment

• Ia. Senecio lautus Solander ex Willd. Sp. Pl. 3: 1981. 1804. (ssp. lautus).

• S. lautus Sol. Prim. Fl. N.Z., unpublished MS., after 1771.

• S. lautus Forst. Fl. Ins. Austral. Prodr. 1786. nomen nudum.

• ?S. angustifolius Forst. (non L.) Fl. Ins. Austral. Prodr. 1786. nomen nudum.

• S. neglectus A. Rich. Essai Fl. Nouv.-Zel. 258. 1832.

• S. australis var. β unidentatus DC. Prodr. 6: 374. 1837. (Cited for N.Z. and Tasmania)

• pro parte.

• S. lautus var. α lautus Hook. f. Fl. Nov.-Zel. 2 (1): 145. 1853. pro parte.

• S. lautus var. α Cheesem. Man. N.Z. Fl. 373. 1906 (including carnosulus).

A varible, much branched glabrous to villous annual or short-lived perennial herb; the prostrate to ascending branches 15–35 cm long, leafy throughout, the stems often purplishpigmented; lower leaves lance-ovate in outline, entire to sparingly toothed, petiolate, often withering early; middle cauline leaves 3–6.5 cm long, lance-ovate to oblong in outline, deeply once-pinnatifid, the principal lateral lobes remote, narrowly oblanceolate or linear, these lobes frequently entire or sparingly toothed, the lamina in the sinuses between the lobes usually entire; terminal lobe usually larger than the lateral lobes; upper leaves reduced, sessile, with a lacerate or nearly entire auriculate clasping base; heads cylindric, borne loosely at the ends of branches throughout the plant; involucre 4.5–5.5 (7) mm high, the bracts numbering 11–13, villous at the often black tips; disk 5–10 mm in diameter; the ligules about 13, yellow, narrowly elliptic-oblong (3.5) 5–7 (9) mm long, rarely shortened and barely exceeding the involucre, 1.3–2 (2.7) mm wide; cypselas 2.5–3 mm long, grooved, strigose overall or merely in the grooves; n=20. Fig. 2.

Senecio lautus had had an exceedingly confused nomenclatural history. This confusion stems from several sources, including application of the name to many Australian texa, application of the name to other New Zealand species, and bibliographic and historical erros. The synonymy is difficult to work out since many of the early collectors were not careful in their notations on specimens. Original material of all the names listed in the synonymy has been seen with the exception of the De Candolle specimen.

The type specimen of the species is No. 15757 in Willdenow's herbarium preserved at Berlin-Dahlem; isotypes are at Kew and the British Museum (Natural History). In his cursory description of the species Willdenow (1804) cited only the Forsters' specimens and indicated the range of the species as simply New Zealand. Photographs of the Willdenow types of both Senecio lautus and S. australis were furnished through the kindness of Dr. G. M. Schulze of Berlin-Dahlem. The photograph of the fragment of Senecio australis leads to the conclusion that this name should probably not be considered synonymous with S. lautus since there is little resemblance between the two specimens. Schulze wrote that these specimens had been given Willdenow by Sprengel; according to Merrill (1954) Sprengel's specimens were originally from the Forster collections. Thus the lineage would appear to be quite clear. However, in 1826 Sprengel listed Senecio lautus and followed his short descriptive paragraph with the obscure statement “Falsum habet Willd.”. Since this remark applies to the holotype it could have considerable importance were its significance known. At the present time an acceptance of the Forster specimen as valid would seem to be the wisest course to follow. Duplicates of this collection are at Kew and the British Museum (Natural History) and closely resemble the Willdenow specimen.

The type locality is unknown, but the ships carrying J. and G. Forster anchored at Dusky Bay for some weeks and in Queen Charlotte Sound on three occasions Since the type collection was made just as the plants were coming into flower, it is likely that the collection was made by the Forsters on their second (November) visit to the Sound.

D. Petrie (WELT); Shingle slip, limestone hill between Broken and Porter rivers, Leonard Cockayne, Dec. 29, 1890 (WELT); Limestone rocks, Trelissick basin, 2,800ft, T. Kirk (WELT, 1908); Mts. behind Castle Hill, Canterbury, TFC, Jan., 1883 (AK 10597); Mt. Torlesse, open places, 2,500ft, 4/09 H. H. Travers (P); Mt. Hay, Two Thumb Range, Barker 352 (CHR 20454); S. Pisa Range, Jan., 1923, A. Wall (Canty); Mt. Arnould, ca. 2,800ft, D. Petrie (WELT, 1908); Dunstan, approx 3,500ft, I. A. McNeur 25/12/1949 (CHR 68905); Eweburn Valley, ca. 2,000ft, 10/1/11, D. Petrie (WELT).

Breeding System

An understanding of the breeding system of an organism may aid in interpreting the variation pattern in a taxon and may give some clues as to the limits and evolutionary potentialities of the group. For most of the flowering season the majority of the taxa of Senecio discussed in this paper are outbreeding. Flowering plants are visited on warm days by hover-flies (Syrphidae) and to a lesser extent by honey bees and bumblebees. The large number of hybrid seedlings on the benches under the plants in the greenhouse lends some support to the idea that most taxa are outbreeding, and further suggests that the pollinators of Senecio do not respect the boundaries of taxonomy or of ploidy in their activities.

Despite this primarily outbreeding nature, all the taxa are self-compatible. It appears that Senecio glaucophyllus ssp. discoideus and S. lautus ssp. carnosulus normally set a high percentage of selfed fruits. Furthermore, the sequence of events in the maturation of florets of all species is such that self-pollination will eventually occur if no pollinator makes a visit. This suggests that in poor weather, when pollinators are not active, self-fertilisation may be frequent. This combination of outbreeding and inbreeding is undoubtedly chiefly responsible for the mosaic of variation characteristic of most of the taxa of the Senecio lautus complex.

Apomixis has not been demonstrated in any of the species; emasculated heads of caged plants set no fruit.

Chromosome Numbers

Although other numbers forming an aneuploid series have been reported, most of the Senecio species which have been investigated by various workers have diploid chromosome numbers in multiples of 10, ranging from 20 to 180 (Darlington and Wylie, 1956). The four species investigated in this paper are polyploids at various levels. For Senecio lautus, n = 20; S. sterquilinus, n = 20; S. radiolatus, n = 40; and for S. glaucophyllus, n = 50. Chromosome numbers were determined from squash preparations of microsporocytes stained with aceto-carmine. Meiosis was regular in all species. Buds were preserved in a fixative consisting of 3 parts 95% ethyl alcohol and 1 part glacial acetic acid.

Following in a list of plants which were used for the chromosome counts, the localities from which they were taken, and their collectors:

Senecio lautus ssp. lautus, n = 20: Motuhoropapa Island, Hauraki Gulf, Geo. W. Mason; Bream Head Peak, Whangaeri Head, Geo. W. Mason; Little Barrier Island, Graeme Ramasay; Cape Turnagain, N. L. Elder; Paekakariki hill summit, R. Ornduff, Mana Island, R. Ornduff; Red Rocks Stream, near Wellington, R. Ornduff; Makara Beach, R. Ornduff; Pencarrow Head, near Wellington, R. Ornduff; Rimutaka summit, R. Ornduff; Mable Island, near Picton, R. Ornduff.

Senecio lautus ssp. carnosulus, n = 20: Punakaiki Beach, I. W. Davey; Black Head, Dunedin, G. T. S. Baylis.

Senecio sterquilinus, n = 20: Brothers Island, Cook Strait, R. Ornduff.

Senecio radiolatus, n = 40: Chatham Island, E. A. Madden.

Senecio glaucophyllus ssp. glaucophyllus, no count.

Senecio glaucophyllus ssp. basinudus, n = 50: near Lake Ellesmere, J. W. Dawson; Allans Beach, Dunedin, G. T. S. Baylis.

Senecio glaucophyllus ssp. raoulii, n = 50: Moemoe, northwest Ruahines, R. Ornduff et al.; Pohatuhaha, N. L. Elder; Ngauroruru, N. L. Elder; Titiokura, N. L. Elder.

Senecio glaucophyllus ssp. discoideus, n = 50: Blue Cliffs Station, near St. Andrews, Mrs. P. R. Woodhouse.

Artificial Hybridisations

Crosses were made in all possible combinations of the four species discussed in this paper, and among all the infraspecific taxa. No living plants of Senecio antipodus were available. Since three of the species represent different levels of polyploidy, it would be expected that hybrids between them would be highly sterile as was the case. These interploid hybrids formed no viable pollen at all. However, hybrids between Senecio lautus and S. sterquilinus, both of which have the same chromosome number, were as fertile as their parents.

The hybrids obtained from the intraspecific crosses were of special interest because they indicated that despite the high degree of variation within the species, nearly all the infraspecific categories are highly interfertile. In a few instances, there is a reduction of fertility in the second generation. Fertility of the hybrids was determined by scoring stained and non-stained pollen grains mounted in cotton blue-lactophenol.

Since the four species are highly self-compatible, particular care had to be taken to prevent self-pollination during the course of the hybridisations. The heads of the seed parents were emasculated by removing the upper portions of the heads with a razor blade, thus removing the anthers but not the stigmas. The heads were then bagged until the stigmas were receptive, and then the pollinations were made. If the pollination was successful, the stigmas withered within a few hours and the cross was considered effected. The species of the Senecio lautus complex are freely crossable under greenhouse conditions, although such free crossability is not a universal feature of the genus.

The results of these breeding experiments show that individuals of three of the four species investigated here are intersterile. In addition to this effective isolating mechanism, S. glaucophyllus and S. radiolatus are completely allopatric, one being mainland and the other an insular endemic. Senecio lautus is spatially isolated from S. glaucophyllus over most of its range, although it occurs within the range of S. glaucophyllus ssp. basinudus in parts of the South Island coast. Senecio lautus and S. radiolatus are both found on the Chatham Islands. Senecio sterquilinus is presumably spatially isolated from all the other members of the complex and is endemic to a unique edaphic situation. Its close relationship to S. lautus is unmistakable on grounds of morphology and high hybrid fertility, and if the two were to occur together in nature a certain amount of hybridisation would be expected.

Senecio sterquilinus is treated as a distinct species because of the relatively large number of characters by which it differs from S. lautus. While hybridisation between these two species, if it does occur, could have a profound effect on their future evolution it would not necessarily affect their present taxonomic status.

The infraspecific taxa which are recognised within two of the species are generally compatible with one another. Consequently, the factors which serve to keep the subspecies of a species distinct over most of their range must be their different ecological requirements combined with spatial isolation. Intermediate forms do

occur, especially in S. glaucophyllus, but since genetic segregation does not occur when these intermediates are grown in cultivation it appears that these intermediates are stabilised biotypes.

The relationship of Senecio lautus to S. glaucophyllus is inferred from the morphological similarity of some of the subspecies of these species. One cannot assume a very close genetic relationship, however, because of the different chromosome numbers of the two species. It is possible that S. glaucophyllus originated long ago as an amphiploid hybrid between a lautus-like ancestor and a form similar to some of the 30-chromosome-pair species now in the New Zealand flora (latter chromosome numbers supplied by J. B. Hair in litt.).

Senecio radiolatus and S. antipodus appear to be more closely related to each other than to any other species. Kirk (1899) compared the latter species with the Fuegian S. candidans, but the resemblance is slight indeed.

The Relationship of the New Zealand Senecio lautus Complex to
Australian Taxa

Many authorities have used the name Senecio lautus to apply to a remarkable diversity of Australian forms. All of the herbarium specimens of “Senecio lautus” and its allies in the National Herbarium of New South Wales, Sydney; the National Herbarium of Victoria, South Yarra; the State Herbarium at Perth; Kew; and the British Museum, Natural History, were examined. In addition, the few Australian specimens in American herbaria were examined.

Nine seed collections of “Senecio lautus” from New South Wales, Victoria, Tasmania, and Western Australia, representing extremes of morphology and habitat, were sown in the greenhouses at the University of Washington in Seattle. All oof the plants which developed were found to have haploid chromosome numbers of 20. These plants were utilised in reciprocal crossing experiments with Senecio lautus ssp. lautus and S. sterquilinus. The range in fertility in the hybrids was between 10% and 70%, with the average about 50%. In addition to this partial sterility barrier there is a definite morphological discontinuity between the array of Australian forms and the relatively more homogeneous New Zealand forms.

It is concluded, therefore, that the interests of taxonomy would be best served by the exclusion of the Australian forms from the limits of Senecio lautus. The Tasman Sea provides an effective barrier to gene exchange between populations in the two countries and provides a convenient taxonomic boundary as well. To include any of the Australian forms in S. lautus would be unwise, since the transition from somewhat similar Australian forms to quite different races in Australia is gradual and would result in considerable taxonomic confusion. Consequently, Senecio lautus, already sensu latissimo, is considered a New Zealand endemic.

Bibliography

Cheeseman, T. F., 1888. On the flora of the Kermadec Islands. Trans. N.Z. Inst. 20: 151–181.

— 1896. On some additions to the New Zealand flora. Trans. N.Z. Inst. 28: 534–537.

— 1906. Manual of the New Zealand flora. Wellington, Govt. Printer.

— 1925. Manual of the New Zealand flora, 2nd ed. Wellington, Govt. Printer.

Chilton, Chas., ed. 1909. The Subantarctic Islands of New Zealand. Wellington, Govt. Printer.

Plant Communities of the Mokohinau Islands, Northern N.Z.

By Mary E. Gillham Department of Botany, University of Melbourne

The group consists of about 12 islands and a scatter of reefs with Fanal Island (not visited) lying approximately 6 miles S. E. of the main group. The largest, Burgess Island, is between ⅝ and ¾ ml. long, about ¼ ml. wide and covers approximately 400 acres. The relative size of the others in the group can be seen in Fig. 1.

II. Geology And Soil

The rocks are igneous with the exception of a small patch of raised beach conglomerate at the landing place. The group is part of a chain of volcanic islands and rises to 366ft (112 m.) above sea level at the Burgess Island lighthouse. Burgess

Figure 1
Mokohinau Islands. Map Showing Location of Seabird Colonies, Transects and Soil Sample Areas

Island consists of an extrusive cumulo-dome of glassy rhyolite of late Pliocene age surmounted by pyroclastic rocks and intruded by rhyolite dykes and the andesite plug on which the lighthouse stands (Fleming, 1950).

Non-organic soil exposed and eroding on the cliffs is of sandy or gravelly texture but most of the island soils have a fair amount of incorporated humus. Of 15 samples tested all were on the acid side of neutral, the pH ranging from 5.2–6.6 (average, 6.1). Readings are inserted in the appropriate localities on the map in fig. 1.

III. Rainfall And Exposure

The annual average rainfall is from 32–33in but only 9in had fallen in 1957 up to the middle of August and little more was expected, as the summers from August onwards are generally dry. In 1956, however, 60in had fallen, the highest total since records were first kept by the lighthouse personnel 20 years previously.

Heavy seas from the Pacific Ocean strike the northern and eastern coasts of the island, but a certain amount of protection is afforded in the W. and S. by Northland and Great Barrier Island. The exposure suffered is much greater than on the forested island of Little Barrier, 20 miles to the S., but Fanal Island supports a covering of bush. Nevertheless, the small patches of relict bush on Burgess Island.

are confined to sheltered, W. facing slopes, suggesting that, once cleared, bush species may not readily regenerate in the most exposed situations. Even the most salttolerant species, pohutukawa (Metrosideros excelsa), taupata (Coprosma repens) and ngaio (Myoporum laetum) showed signs of severe salt scorching more than 200ft (61 m.) above sea level and a considerable distance from the coast.

In a recent severe N.W. gale the sea had broken across the low-lying part of the island between the Blowhole and the landing beach and transformed the freshwater marsh there into a brackish one. The water level rose and all existing foliage was killed, regeneration not taking place until several months had elapsed (Smith, in lit.).

IV.—Burning And Grazing History

The islands were previously inhabited by Maoris, whose descendants return annually for the mutton bird harvest. It seems likely that either regenerated or original forest remained after Maori occupation; this was probably destroyed subsequently by fire rather than by grazing, although both would have contributed towards preventing its regeneration (Tohana in lit.).

There had been no burning for many years when the lighthouse was erected in the early 1880s, but the vegetation was quite open (Anderson in lit.).

An early lighthouse keeper, Sandager, writing in 1889, listed 7 woody species as important constituents of the vegetation (Carmichaelia, Coprosma, Metrosideros, Myoporum, Olearia, Pittosporum and Veronica), but stated that these were more or less scattered and stunted owing to the lack of shelter. In 1957, Olearia and Pittosporum were not recorded, Veronica (Hebe) was seen only on the smaller ungrazed islands and only 1 tree of Carmichaelia was found on Burgess Island (more on the western isles) suggesting a further reduction in woody species during the past 70 years.

From at least as early as 1920 the lighthouse keepers grazed stock on Burgess Island and burned the vegetation at intervals of approximately three years to keep the sedges (Mariscus and Scirpus) in check. In 1932 Trig Island and Maori Bay Island in the W. were burned by fishermen (Anderson in lit.) the vegetation having regenerated in the subsequent 25 years to a flax (Phormium) community with scattered shrubs.

It is fairly certain that grass seeds (Paspalum and Stenotaphrum and probably also Lolium and Dactylis) were broadcast on Burgess Island after burning (Anderson in lit.) and these now occupy a considerable area.

V.—Vegetation

the bush and the buffalo-grass of the flat across which came winds from the quarter with the smallest distance of fetch. Lighthouse Hill gave shelter from winds from the Pacific.

The bush occupied a low steep cliff and the boulders at its foot and was accessible to grazing animals which had severely pruned the Macropiper

Its preservation as the only inland community of native bush which had escaped the depredations of fire and grazing livestock on Burgess Island, suggested that the constituent species might be more resistant to these two suppressive factors when not having to suffer the added rigours of exposure to the worst salt-bearing winds. It is of interest in this connection that the only two stands of Metrosideros surviving on grazed parts of Burgess Island were on sheltered W. facing cliffs near the Cauldron in the N. and Pohutukawa Gully in the N.W., whereas on the ungrazed islands the species occured also on exposed cliffs.

The presence of the garden species Viola odorata and Zantedeschia aethiopica and the proximity of the old tapu Maori grave in a walled, overgrown garden a few hundred yards away, suggested that this sheltered locality, near the only beach where it was practicable to make a landing, might have been occupied by a former island community.

With the exception of Blechnum and Pyrrosia, both of which were rare on the islands, the following species were recorded only in this mixed bush:—

3. Flax Communities

All but the lowest of the smaller, ungrazed islands were dominated by Phormium colensoi which formed thickets 4–6 ft. (1–2 m.) high and was scarcely penetrable in places. Metrosideros excelsa was abundant with it, Cassinia retorta, Carmichaelia aligera and Myoporum laetum frequent and Hebe salicifolia and Muehlenbeckia complexa occasional. Important constituents of the ground flora were Arundo conspicua, Pimelea urvilleana, Pteridium esculentum and Scirpus nodosus.

These outer islands had suffered less modification from human occupation than had Burgess Island and the proportion of aliens in the flora was smaller—33% as opposed to 48% on Burgess Island. Less time was spent investigating the outer islands but this would not wholly account for the fact that less than half as many species were recorded there as in the more heterogeneous flora of Burgess Island (54 and 121 spp. respectively).

Isolated flax plants occurred on the more sheltered of the inaccessible cliffs of Burgess Island where they found a refuge from grazing animals rather than because of their affinity for sea spray. Where not pushed back to this marginal habitat by grazing, Phormium preferred slightly more inland situations, giving way to other spp. on exposed coasts (see Fig. 2)

4. Sedge Communities

The two most important Cyperaceous plants on the islands were Scirpus nodosus and Mariscus ustulatus, but an unidentified species of Carex was locally dominant on exposed, ungrazed cliffs.

a. Scirpus nodosus

Scirpus nodosus formed dense swards on the northern, western and eastern peninsulas of Burgess Island most remote from the centres of human occupation. As the latter were approached the Scirpus communities became progressively more

open, with European pasture species growing between the tussocks until they eventually merged into grass pasture with Scirpus occasional or absent.

In the extreme W. Pteridium esculentum was co-dominant with the Scirpus but this became rare on slopes with an exposed aspect. On E. facing coasts the Scirpus became patchier and merged with exposure-tolerant grasses such as Holcus lanatus, finally giving way to belts of halophytic species.

High above sea level on the W. of Trig Island the Scirpus was co-dominant with Phormium and it persisted as an important subordinate species in the main flax communities of the western isles.

b. Mariscus ustulatus

Mariscus ustulatus covered much less ground than Scirpus and occurred mainly on fairly wet ground and cliffs. It was sometimes associated with Scirpus or pasture plants or formed a belt between these and the Leptocarpus simplex or Disphyma australe of the lower cliffs.

The species was apparently fairly plastic in its water requirements, growing on both water-logged flats and well drained slopes. With Leptocarpus simplex and Stenotaphrum secundatum it co-dominated the marsh behind the landing bay, but gave way to Leptocarpus, Cotula coronopifolia, Isolepis cernuus and grasses in the wetter parts of the Cauldron flat which it dominated.

Very little was seen on the western isles where it may have been unable to compete effectively with the ungrazed Phormium of similar but more robust life form.

c. Leptocarpus simplex

Leptocarpus simplex (Restionaceae) dominated not only areas with a high water table but also a number of well drained cliff areas subjected to heavy spray. Its distribution was essentially coastal and the water around its roots was often brackish.

5. Grass Communities

Grass communities were of two main types, almost pure swards of Stenotaphrum secundatum and mixed swards of European grasses and legumes, often associated with Scirpus nodusus. They occurred around the centres of human activity viz:— the landing jetty, the lighthouse, the keepers' dwellings and the S. E. block of the island which was occupied by an R.N.Z.A.F. camp during the World War II.

a. Buffalo grass

The strongly-growing alien Stenotaphrum secundatum occupied the sheltered central valley of Burgess Island, and varied from a lawn-like turf a few cm. high where stock congregated around water troughs, to dense mats 1 m. thick. This last growth habit was that most commonly seen, the top of the mattress-like layer being fairly level where subjected to little wind action but undulating, from 15 to 100 cm. deep where at all windswept, giving local turbulence as in the hummocky Holcus lanatus swards of exposed British clifftops (Goodman and Gillham, 1954). Mariscus ustulatus often replaced the Stenotaphrum locally where there was much falling spray or where the water table rose above the surface seasonally. The Stenotaphrum seemed to approach exposed coasts only in moist areas where falling spray was diluted. The dense growth habit of the plant, however, rendered it fairly immune to spray damage because there were always young shoots pushing up through the protective mat of old ones which might suffer damage in salt storms.

The aggressive growth of the dominant excluded most subordinates and the purity of the swards is illustrated in the accompanying table where Stenotaphrum is seen to form an average ground cover of 94%.

Floristic Analysis of Two Buffalo Grass Communities.

VI. Plant Zonation in Relation to Exposure

Fig. 2 shows the prevalence of coastal belts of halophytes on cliffs with a N.E. aspect. On more sheltered S. W. cliffs these belts are too narrow to be included on the vegetation map but the western cliffs of Trig Island were not explored, so the omission of coastal belts there may be of no significance.

Zonation from the sea upwards on the E. coast of Trig Island where the situation was uncomplicated by grazing was as follows:—

1. Disphyma australe. A. narrow discontinuous strip descending to 3–12 m above sea level, depending on the local topography and exposure.

2. Carex sp. Drooping clumps occupying crevices in the Disphyma zone or on vertical faces higher up where there was roothold for little else.

3. Myoporum laetum. Dense thickets seldom more than 1 m high on steep slopes; sometimes descending to the lower limit of land vegetation, but apparently less spray-tolerant than Disphyma or Carex. Mostly pure but with patches of these 2 spp., Coprosma repens and Phormium colensoi.

4 (a). Phormium colensoi. Dominant of the main slopes with patches of Myoporum in the lower part, Metrosideros excelsa and other spp. in the upper part.

(b). Metrosideros excelsa. Dominant on the steeper more broken cliffs at this level.

5. Muehlenbeckia complexa and Scripus nodosus co-dominant with the Phormium on windswept crests and Pteridium esculentum co-dominant in local shelter. Arunda conspicua and Myoporum quite common.

Leptocarpus simplex frequently replaced some of the Disphyma zone near sea level on the other S. W. islands or on cliff edges 50–80 m high in the N. and E. Other salt marsh plants found 70 m or more above sea level on the N. and E. coasts were Salicornia australis, Samolus repens, Spergularia media, Cotula coronopifolia and Isolepis cernuus, the roots of the last two penetrating the dung pellets of sheep in the rockier situations.

Coprosma repens seemed to be the most exposure-tolerant of the shrubs, as on islands of Cook Strait and Bass Strait (Gillham, 1960b). The leaves of Myoporum laetum suffered severe salt-scorching in almost all localities, but the plants as a whole, though stunted, survived to cover considerable areas. Where the Myoporum was damaged so also were mesophytes such as Plantago lanceolata and some of the native and alien pasture grasses.

Soon after the mat of Stenotaphrum secundatum had been cut away from around the Metrosideros excelsa saplings on Lighthouse Hill the leaves of the young trees suffered severe salt damage in a bad storm, although growing much further from the coast than was normal (Smith, in lit.) A less xeromorphic leaf type than usual, formed in the shelter of the Stenotaphrum, may have contributed to the plants' susceptibility.

Fig. 4 shows zonation of plants in three coastal areas; the boulder beach near the Burgess Island landing, the cliffs of Pohutukawa Gully in the N.W. of Burgess Island and a lower-lying Metrosideros community in the N.E. of Maori Bay Island.

Fig. 5 shows cliff zonation in four other localities: transect VII from Disphyma through the alien Dactylis, Lotus and Holcus to pasture containing native Muehlenbeckia, Oxalis and Dichondra: transect VIII from Disphyma through the alien Lotus, Lolium and Holcus to the native Scirpus: transect IX from Disphyma through Lotus, Holcus and the native Leptocarpus and Pimelea to cassinia scrub: transect X. from Myoporum, Disphyma and Arundo through Pimelea and Muehlenbeckia to Phormium, Scirpus and Carmichaelia with aliens unimportant (see Fig. 1 for localities).

VII. Relationship of Vegetation and Grazing Animals

1. Grazing

In August, 1957, Burgess Island supported a small herd of about 12 dairy cattle, a herd of feral goats numbering not more than about 30, and a few pigs, the sheep having been removed the previous March.

The goats lived mainly on the N.E. segment of the island, which was accessible only by a narrow isthmus and not visited by the cattle, but they made occasional sorties along the northern cliffs to the W. Some of the cattle were pastured on the European grasses between here and the lighthouse, one of the bulls shared the central of the five northern peninsulas with the pigs and the milking cows had the run of the rest of the island except for part of the inland face of Lighthouse Hill.

During the winter, the dairy, cows fed mainly at night, resting on the Stenotaphrum of the “home paddock” during the day but grazing very little. After the evening milking they drank at the troughs in the Stenotaphrum of the landing flat, then dispersed W., N.W., and S.E. to the areas occupied by European pasture spp. and Scirpus nodosus. They grazed their way outwards, eating the grasses and legumes and reaching towards the edge of the more peripheral zones of pure Scirpus

Where livestock converged on a gateway across the narrow neck of land N. N.E. of the lighthouse the ground was 75% bare, even during the moist winter season. The three natives, Dichondra repens, Disphyma australe and Senecio lautus were the most abundant species in this more maritime environment and only 61% of the 18 spp. recorded were aliens.

Of the 18 spp. growing among the short trampled Stenotaphrum around the water troughs all were aliens.

Species surviving trampling were all of low growth habit and many were hemicryptophytes, those normally having tall inflorescences (e.g., Cirsium, Erigeron and Rumex) producing either stunted ones or none at all.

3. Manuring

Species stimulated to robust growth on the heavily dunged soil around the stockyard were Amaranthus lividus, Chenopodium murale, Malva rotundifolia?, Modiola caroliniana and Phytolacca octandra—all aliens.

A characteristic seedling flora occured on each of the many patches of cow dung along the top of the boulder beach. It had nothing in common with the Muehlenbeckietum of the community as a whole and the seeds had probably arrived with the dung and germinated more or less simultaneously to give an even stand a few cm high Ninety-one per cent were aliens (unless Geranium dissectum be regarded as cosmopolitan) although only 40% of the beach spp. were alien:

VIII. Gull Colonies

Mokohinau was described by Fleming (1946) as the chief breeding place of the red-billed gull (Larus novae-hollandiae) in the North Auckland area apart from the Three Kings Islands. He estimated the 1944 population as consisting of approximately 8,000 birds; Buddle (1947a) estimated the 1945 population as 18,000–20,000 birds, of which 13,000 were breeding.

The gulls were resident on the island from the end of August until March. Thus for about seven months each year certain areas of vegetation were subjected to trampling and disturbance and their floristic composition modified accordingly. During the intervening five months, which coincided with the moister winter growing season, there was considerable regeneration of an annual flora which was largely destroyed when the birds returned in early spring. There was, in addition, more permanent regeneration in vacated areas due to local changes of nesting site from year to year.

For the years 1944 and 1957 nesting colonies are plotted in Fig. 1, and a S. W. coast site occupied in 1936 (Buddle, 1947b) but not necessarily representing

the entire population, is also included. Buddle reported considerable variations in nesting sites between 1944 and 1945, with some of the northern colonies enlarging and coalescing.

The vegetation able to perennate in the gull colonies throughout the breeding season was largely halophytic and Disphyma australe was particularly characteristic, covering large areas up to and above 60 m above sea level on the northern cliffs where the gulls were numerous. This species was equally characteristic of other types of seabird colonies in New Zealand and S. E. Australia (Gillham, 1960a). In many colonies Disphyma formed a continuous mat broken only by circular patches where nests had been built on top of it. The nest material had dispersed by the time the birds returned in the subsequent year and the patches were still largely bare, but tentative colonisation by the following species had occurred:–

Mariscus ustulatus survived well in the gull colonies but Scirpus nodosus was much less conspicuous, although often dominant of the surrounding terrain.

Floristic composition of the gull vegetation was analysed by means of valence squares and transects, and the results are summarised in Fig. 6. The analyses were carried out when the cyclic succession had reached its most advanced state—at the end of the growth period when the birds were returning in the latter part of August to initiate the destructive phase.

The native halophytes, Disphyma australe and Senecio lautus were the most constant species, showing 76% and 74% frequency in 130 valence squares and 86% and 82% frequency in the 50 squares of the two belt transects. Bromus catharticus (44% and 48% frequency) was the most characteristic of the aliens (cf. tern and gannet colonies of New Zealand and Australia, Gillham, 1960a).

Many of the European pasture species appeared to benefit from the enhanced fertility of the gull colonies in the less exposed areas (4–8 in Fig. 6) but the American Buffalo grass seldom occurred in nesting colonies. A lush growth of Parietaria debilis was typical of well manured crevices but was rare away from the gulls on Mokohinau (although growing as a boulder beach species on Little Barrier and a woodland species on Bass Strait islands).

A vacated black-backed gull's nest (Larus dominicanus) in a Metrosideros-Phormium community was occupied by lush Tetragonia trigyna with Asplenium flaccidum, Bromus catharticus, Chenopodium allani, Stellaria media and Trifolium repens.

IX. Petrel Colonies

The grey-faced petrel (Pterodroma macroptera) is the most abundant burrowing bird of the Mokohinau group. No attempt has been made to estimate its numbers, but Buddle (1947a) states that it is well distributed over all the islands, particularly the three western ones. This is the northern mutton bird, and 3,000–3,500 chicks are taken annually by Maoris during the early part of December (Sandager, 1889, and Buddle, 1947a); a large proportion of the catch at present comes from Fanal Island. Burgess Island colonies are mapped in Fig. 1, but no survey was made on the western islands, only those burrows seen at the head of Maori Bay being indicated on the map.

As long as the soil was of sufficient depth and suitable texture for burrowing, the petrels seemed little concerned as to what plants they burrowed among, and the 11 areas investigated were occupied by 11 different plant communities, ranging

Riblet Frequency as a Taxonomic Character in New Zealand
Terrestrial Mollusca

By R. A. Cumber

Cavellia biconcava (Pfeiffer) (Charopidae) Tauherenikau Valley, 1938.

Ptychodon hunuaensis Suter (Charopidae) Clevedon, 9.7.58.

The information on variation is given in a number of forms. It is seen that the range in counts increases with successive whorls except in the case of Suteria ide which instance is unlikely to be significant. In all cases the standard deviation is lowest in the first post-nuclear whorl and rises sharply in the second. In all except one there is a further but often less-prouounced rise in the third whorl (Fig. 1). In the seven genera studied, significant correlations between whorls occur four times in the cases of whorls 1, 2 and 1, 3 and six times in the case of whorls 2, 3.

Discussion

Riblet frequency is doubtless governed by both inherent qualities and external influences, and just how much each contributes is difficult to assess. In most species the spacing between riblets is not a strictly constant feature although it is often moderately regular. At intervals, from the earliest stages, single spacings or successions of spacings which are wider or narrower than those which follow may occur. A study of the genera which occupy different types of habitat may show that this is reflected in the regularity of riblet spacing. One would expect such genera as Cavellia and Fectola which occur mainly beneath ground materials to show more regularity than is shown by the genera Phenacohelix and Ptychodon which often occupy materials away from ground level, and indeed, this may well be so; but just how much of this variation is inherent and how much is due to the conditions immediately at hand cannot be determined without experiment. These are important considerations in systematics.

Occasionally the number of riblets in the first post-nuclear whorl may equal or exceed the number of riblets in the second whorl in other specimens from the same population. The same may apply in the case of the second and third whorls. Usually, however, there is an increase in the number of riblets in successive whorls. Exceptions to the rule will probably involve specimens which have been injured, or species in which successive whorls show little increase in diameter such as

Phenacharopa novoseelandica (Pfciffer).

The tendency for riblet counts to increase on whorls formed later in the life of the animal is accentuated in many species in old age, and this is a feature which further complicates frequency variations.

Studies on New Zealand Elasmobranchii.—Part X
The Genus Echinorhinus, with an Account of a Second Species,
E. cookei Pietschmann, 1928, from New Zealand Waters^*

By J. A. F. Garrick

Study Material

(a) Adult: Male, 1,980 mm T. L. (Neotype, Dom. Mus. No. 2774) lined from 40–50 fathoms, Palliser Bay (Cook Strait, New Zealand), Aprial, 1959.

(b) Juveniles: Female, 450 mm T. L., male, 445 mm T. L. (Dom. Mus. No. 2792) and male, 472 mm T. L. trawled from Cook Strait, New Zealand, about 1946 or 1947 and held in the Zoology Department, Victoria University of Wellington.

Description

(a) Adult (Text-fig. 1, C, Text-fig. 2, A–J, Plate 7, A–B)

Head depressed, small-eyed, snout pointed. trunk stout, sub-cylindrical anteriorly, markedly compressed posteriorly. Dorsal and ventral profiles of trunk almost parallel. Height of trunk at origion of pectorals about one-sixth of its length to subcaudal origin. Length of body measured to cloaca 63.3% of total length. Caudal peduncle strongly compressed and deep, its depth almost twice its width and equal to snout length in front of eye. No precaudal pits or lateral keels on the peduncle.

Dermal denticles in the form of erect or slightly retrorse thorns with prominent radial ridges extending down on to multiangled bases. The perimeter of each base is deeply indented between adjacent radial ridges so that the numerous angles and ridges are strongly defined. Each denticle carries only one thorn which is sharply pointed, and ridged along all or most of its length. All denticles are solitary, adjacent bases never fused though occasionally contiguous. Diameter of denticle bases mostly 2–3 mm or less, infrequently 4 mm.

Denticles obvious over whole of body excepting underside of snout and around mouth (which regions are essentially smooth, though a few minute denticles are present), small areas at axils of fins, and distal margins of fins. Denticles everywhere wide spaced but more or less uniformly distributed. Largest denticles along dorsal surface of trunk, especially above lateral line; towards ventral surface, and on to head and tail, denticles gradually decrease in size. Several sizes of denticles present, particularly on dorsum of trunk, where minute denticles of uniform size are dispersed throughout larger denticles of various sizes.

Lateral line conspicuous from above 2nd gill-opening to tip of tail as a white furrow with closely approximated edges, the upper slightly overhanging the lower. It is crossed at irregular intervals along its length by narrow, thin, membranous bridges, though considerably more of it is open than is covered Inside the furrow and supporting its walls, are numerous, regularly-placed skeletal elements in the form of incomplete rings, presumably derived from

band along the lower lip. The larger denticles are present chiefly on the dorsal surface of trunk and head, and are well-spaced but more or less regularly distributed, their greatest concentration being above the lateral line between head and 1st dorsal fin; below the lateral line they are less numerous, as they are on the head and snout, on the peduncle and along the proximal part of the epiural lobe of the caudal. These large denticles are newly erupted or erupting, evidently at a fairly rapid rate for the 472 mm male shows considerably more of them than the slightly smaller 445 mm male.

Lateral line a conspicuous white furrow from the 2nd gill-opening rearwards, where it is completely open, without membranous bridges and with its upper and lower edges more separated than in the adult. The supporting skeletal rings have simple (not bifurcated) ends. Lateral line pores on head and snout very prominent.

Head measured to 1st gill-opening 4.4 in total length. Snout length measured to eye 2.4 in head. Eye large, its horizontal diameter 2.4 in length of snout. Spiracle minute, placed little more than an eye length behind eye. Length of 1st gill-opening 1.4 in length of 5th.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Teeth 11 - 10/11 - 9 in the 445 mm male, 12 - 11/10 - 10 in the 472 mm male, one-cusped and similar in the upper and lower jaws. Each tooth with an ovoid to subrectangular base about twice as long as high, and carrying a sharply-pointed, smooth-edged blade-like cusp. The cusps are enamelled only on their margins, and are so strongly reflexed as to lie horizontal; hence their median margins form a continuous cutting edge.

Dorsal fins with convex anterior margins. First dorsal origin just anterior to middle of pelvic base or over anterior third, insertion over or just anterior to end of pelvic base. Height of first dorsal 1.3 in its base. Posterior free corner of 1st dorsal over middle of posterior (inner) margin of pelvic Caudal measured from hypural origin 3.3 in total length. Distal margins of pectorals straight or slightly convex. Length of anterior pectoral margin equal to distance from rear edge of eye to 2nd gill-opening.

Length of pelvic base 1.4 in length of anterior pectoral margin. Claspers reaching only two-thirds of distance from pelvic insertion to posterior free tip of pelvic.

Echinorhinus brucus (Bonnaterre, 1788)

As mentioned above, because of possible confusion between this species and E. cookei, its presence in New Zealand waters cannot be confirmed from any of the five previous records, but instead depends only on the unrecorded mounted skin, 1,420 mm long, in the Otago Museum (Plate 7, C-D). No further data other than its label, “Dunedin, April, 1887”, are available: its condition and probable distortion do not warrant it being used for obtaining dimensions.

The recognition of the Otago Museum specimen as E. brucus rather than E. mccoyi (in which species Phillipps placed his 1946 record of a New Zealand specimen) depends mainly on the recent accounts in Bigelow & Schroeder (1948, p. 527; 1957, p. 135) where they describe sufficient variation in E. brucus to provide for the differences cited by Whitley (1931, p. 311) as the basis for his proposed new subgenus and species E. (Rubusqualus) mccoyi. Phillipps (1946, p. 20) holds that the gill-openings are longer in E. mccoyi than in E. brucus; but these seem subject to considerable variation. Thus while the lengths of the 1st and 5th gillopenings in the type of E. mccoyi are 2.9% and 6.4% of the total length respectively, they are 3.6% and 6.4% in a Mediterranean specimen, and 2.3% and 5.4% in a South African specimen of E. brucus (pers. comm. from Dr. Denys E. Tucker on dimensions of specimens in the British Museum).

The above leaves no grounds on which to separate and Australasian species E. mccoyi from the cosmopolitan species E. brucus. But detailed accounts and dimensions of E. brucus from any localities, including the North Atlantic as well as the Australasian region, are still needed if the currently believed cosmopolitan status of E. brucus is to be assured.

Summary

(i) A. second species of Bramble Shark, Echinorhinus cookei Pietschmann, 1928, is recorded and described from a 1,980 mm male recently caught in Cook Strait, New Zealand. E. cookei has been known only from the type taken off Hawaii, and is generally regarded as synonymous with the cosmopolitan E. brucus.

(ii) E. cookei is not separable from E. brucus in its dimensions, external morphology or teeth, but is strikingly different in its dermal denticles which are numerous, uniformly distributed, small (not more than 4.0 mm basal diam.) and have deeply indented, angular bases and prominently ridged spins. In contrast, the buckler-like denticles of E. brucus are sparse, irregularly distributed, large (up to 15 mm or more basal diam. in solitary denticles but reaching to 35 mm in compound bucklers) with entire-margined bases and finely ridged spines. Adult E. cookei are also almost smooth under the snout and around the mouth, while in E. brucus these areas retain noticeable-sized denticles.

(iii) The Bramble Shark recorded off California by Hubbs & Clark (1945) as E. brucus is shown to be E. cookei. This confusion between the species, due to inadequacies in the earlier accounts of E. brucus, suggests the need for examination of other records of E. brucus. In this respect none of the five records of E. brucus from New Zealand are sufficiently definitive to allow confirmation as to species; but E. brucus is established as a member of the New Zealand fauna by the mounted skin of a Dunedin specimen in the Otago Museum.

(iv) Three juvenile specimens of E. cookei from Cook Strait are also described. These are markedly slender in comparison to the adult, and have one-cusped teeth as in Squalus. Their dermal denticles agree in relative size, spacing and distribution with those of the adult.

(v) The lateral line of juvenile and adult E. cookei is an open furrow from above the 2nd gill-opening rearwards. Its walls are supported by incomplete skeletal rings whose free ends project rearwards as spines along the edges of the furrow. In the adult the furrow is bridged at irregular intervals by narrow cross-connections of skin.

(vi) As the type of E. cookei is no longer in existence, the 1,980 mm male (Dom. Mus No. 2774) from Cook Strait is designated as the neotype of this species.

Acknowledgements

Various people have assisted with this study; some are acknowledged throughout the text, but others I. would like to thank are Dr. R. R. Forster, Otago Museum, for the photographs of E. brucus, and Mr. F. O'Leary, Dominion Museum for those of E. cookei used in this account, those members of the Dominion Museum staff who assisted with the preservation and handling of the New Zealand adult specimen of E. cookei, and lastly Professor L. R. Richardson, Department of Zoology of this University, for continuing encouragement, suggestions and advice.

Literature Cited

Bigelow, H. B., and Schroeder, W. C., 1948. “Fishes of the Western North Atlantic, Part I” Mem. Sears Found. Mar. Research, No. 1, Part 1, pp. 59–576, Text-figs. 6–105.

Bigelow, H. B., and Schroeder, W. C.— 1957. “A Study of the Sharks of the Suborder Squaloidea,” Bull. Mus. Comp. Zool., 117 (1). 1–150, Pls. 1–4, Figs.

Blainville, H. M. D. DE, 1816. “Prodrome d'une nouvelle distribution systematique du regne animal.” Bull. Sci. Soc. Philomatique, Paris, pp. 105–124.

Blainville, H. M. D. DE 1825 “Vertebres, classe 5, Poissons”. In Viellot, Desmarest,… Faune Francaise… Vol. 1, Part 3, 96 pp., 120 plates.

Bonnaterre, P. J., 1788. “Ichthyologie”, in Tab. Encyc. Method des trois Regnes de la nature Paris lvi + 215 pp., Pls. A, B. + 1–100.

Fowler, H. W., 1941. “The Fishes of the Groups Elasmobranchii, Holocephali, Isospondyli, and Ostariophysi… Contributions to the biology of the Philippine Archipelago and adjacent regions.” U. S. Nat. Mus. Bull. 100, Vol. 13, × + 879 pp., 30 text-figs.

Ascidians of New Zealand Part XIII-Aseidians of the Cook Strait Region

By Beryl I Brewin, University of Otago