[Presidential Address to the Philosophical Institute of Canterbury, 7th November, 1894.]
No paper of a general kind about our seaweeds accessible to the ordinary reader has appeared since the publication of Hooker's “Handbook of the New Zealand Flora” in 1864. I have, therefore, thought that this would be a fitting opportunity to summarize some recent results, and to attempt to show the chief characteristics and affinities of the species inhabiting our shores. This, as you know, has already been done for our flowering plants, but no endeavour has been made as yet to compare our seaweeds with those of other botanical districts. Of course we cannot expect the broad generalizations from such a comparison that we get in the case of flowering plants, but I think the results, whether negative or positive, will be sufficient to justify the labour, particularly as the subject of the distribution of the marine Algæ has received considerable attention recently.
In Hooker's Handbook the number of species of marine Algæ described is 317, made up thus: Chlorophyceæ, & c., 40; Rhodophyceæ, 219; Phæophyceæ, 58. After the publication-of this book no work was done among our seaweeds until in the early seventies Dr. Berggren, of Lund University, carefully collected them in all parts of the colony. His collections were handed over to the great algologist, Professor J. G. Agardh, who in 1877 published an annotated list of our species under the title * “De Algis Novæ Zealandiæ Marinis.” In 1892 Professor Jeffery Parker, F.B.S., of Otago University, sent a small collection of New Zealand Algæ to Professor; Harvey Gibson, of Liverpool. This collection is described in the “Journal of Botany,” vol. xxxi., No. 366. No other work of a general character has, so far as I am aware, been done
[Footnote] * The specific names of this list have been adopted throughout the paper where no authority is given.
on our seaweeds since they were described by Harvey in the “Flora Novæ Zealandiæ.”
Agardh's list is not quite complete, as it takes no note of Corallines, of which twelve are recorded in the Handbook. The total number of species included in it is only 277, or forty less than those given by Hooker. On the other hand, forty-four of the species included are new to our Islands; and, of these, thirty-nine are new to science, and consequently are, as far as we know, endemic; and three others—Ceramium nodiferum, Gigarfina laciniata, and Gracilaria flagellifera—are only known from the Chathams, which appear to be richer than much of the neighbouring mainland in species. The two lists therefore include about 283 species in common. Agardh's list, on adding to it the Corallines of Harvey and Hooker, excludes about seventy-two of the species described in the Handbook. It is difficult to be positive about the exact number, as sometimes one species in one list will correspond in part to two or three in the other. Again, there must be added to Agardh's list two species—viz., Ceramium, stichidiosum, Asparagopsis armata—omitted from it probably by an oversight, as they are admitted by him into our flora elsewhere.* However, after making these additions, the discrepancies between the two lists still remain rather large. Perhaps it would be well here to remind you of the following passage from Hooker's preface to the Algæ in the Handbook:† “To my late friend Dr. Harvey I am indebted for the determination and description of the New Zealand Algæ in my Flora of these islands. His widely and deeply deplored death during the present year has deprived me and this work of the benefits of his revisal of the following compilation.”
It is quite possible that had Dr. Harvey lived some of the discrepancies between the lists referred to above would have disappeared—some of the species incorrectly included in the Handbook would probably have been excluded. Thus, for example, the well-known Sargassum bacciferum, or gulf-weed, appears in it on the authority of D'Urville, Lesson, and Sinclair. Its appearance is possibly due to the imperfect description of imperfect specimens. ‡ Turbinaria, Phyllospora, and Scaberia, on the other hand, may have crept in on account of their occurrence in Australia. Early writers were not always, careful to distinguish between Australia and Australasia. None of these genera have been found by any recent collector in New Zealand, and, as the species are all large and conspicuous, they would certainly have been obtained recently,
[Footnote] * “Epicrisis Sysfematis Algarum,” p. 106 and p. 666.
[Footnote] † “Handbook of the New Zealand Flora,” p. 639.
[Footnote] ‡ Vide “Systematic and Structural Account of the Genus Turbinaria,” by Miss E. S. Barton: Trans. Linn. Soc., Oct., 1891.
even if comparatively rare or sporadic, whereas both Scaberia and Phyllospora, are stated to be common in the Handbook, although no precise locality is given. * Lessonia fuscescens I have dealt with elsewhere. After excluding such intruders we find Agardh and Hpoker in practical agreement as to our Phæophyceæ, which we may now say are comparatively well known. The chief points of difference still remaining are the introduction by Agardh of two previously unknown species of Elachista and four new Cystophoræ, making his list of Phæphyceæ fifty-three, while Hooker's stands at-fifty-eight. Further alterations will no doubt be chiefly towards a better discrimination of species and varieties. This is wanted especially in the genera Carpophyllum and Ecklonia, and probably also in Cystophora.
On turning to the Chlorophyceæ we find thirty-seven in Hooker, of which, however, several belong to fresh water-Agardh has only twenty-four, and of these only two are new. He has rejected, therefore, about fifteen of Hooker's species. Of these, several are fresh-water plants but on excluding these there still remain about eight species which do not occur in Agardh's list. These are either varieties of recognized forms or minute plants belonging to the lower orders. I have; however, seen several minute Chlorophyceæ which I could not assign to any of Agardh's species. It may be regarded ascertain that some small green seaweeds still remain to be discovered. I have here, and throughout the paper, omitted the Protophyceæ from consideration, as they are but little known.
On turning to the Rhodophyceæ, we find the divergences existing between the two authorities are very numerous. Many of them of course are only differences of classification due to our increased knowledge of the methods of reproduction; many others are differences in synonyms; but when these are eliminated there still remain a large number to be accounted for Thirty-five new species have been added by the recent writer. As the total number in his list is 195, on allowing for the Corallines we find he has evidently excluded about fifty of Hooker's species. Again, it may be remarked that it is difficult to give the exact number, as it is not always possible to trace the correspondence of specimens under-different names, and as many of Agardh's identifications of Harvey's species are marked with a (?). It would not serve any useful purpose at present to investigate in detail the points of difference between, them, as it would be impossible in many cases, without access to type specimens, to form an independent judgment about the point at issue. What I wish to do is to determine within what possible limits of error our
[Footnote] * Trans. N.Z. Inst., vol. xxvi.; p. 304.
knowledge is reliable, so that in the succeeding portions of the paper no ill-considered generalizations may be indulged in.
Unfortunately, neither Harvey nor Agardh ever visited New Zealand, and consequently they have only seen our plants in the dried condition; but the latter, doubtless inheriting his father's rich collections, and having received duplicate types of most of the species described throughout the century, has had a far wider range of specimens to work upon than Harvey, who, however, had examined the Australian marine Algæ in the living condition during a stay of some months there. Agardh, again, has been for-many a year, and still is, the chief living authority on the morphology of the Algæ, and his list undoubtedly represents a far closer approach to accuracy than that of the Handbook. It must be noted also that it is in no way a compilation, as the other was. He has only inserted in it a few species not collected by Dr. Berggren, and these upon the best authority. It may be fairly assumed, under these circumstances, that very nearly all of the species enumerated in it are genuine, and inhabitants of our shores. On the other hand, it is quite impossible to say how many of the fifty species excluded may Again be found here. Against many of them the primd facie evidence is strong. Amongst them are no less than eleven species of Polysiphonia. This is the largest and most difficult genus of Rhodophycæ to discriminate, and there must always be much uncertainty as to the exact delimitation of its species. Another dozen have only been collected at the Auckland Islands, and the majority not at all since D'Urville's expedition. Taking all things into consideration, it is probably correct to assume that at least two-thirds of Agardh's “species excludendæ” have been rightly thrown out. On the other hand, we may be satisfied that those species which have survived the criticisms of two such competent judges as Dr. Harvey and Professor Agardh, working in complete inder pendence of each other, are genuine. Undoubtedly a considerable number of Rhodophyceæ still remain to be discovered—in fact, I have now some undescribed species. Even in Britain itself fresh indigenous species are still being, brought to light, and certain kinds of Algæ (e.g., shell-boring species) have not even been looked for here.
The collection sent Home by Professor Parker included fifty-one species, of which one only (Rhodocorton parkeri, Gibson) is new to science. Professor Harvey Gibson seems to have fallen into a strange mistake with regard to the habitat of this plant. He states that he obtained it “growing at the base of a cluster of molluscan (?) eggs.”* Thanks to
[Footnote] * “Journal of Botany,” June, 1893, p. 163.
Professor T. J. Parker, I have seen one of the type specimens, and I find that the plant is epiphytic on the well-known Algæ, Lychæ (Conferva) darwinii, Kuetz; This being somewhat decayed has perhaps caused it to be mistaken for molluscan eggs. Professor Gibson's list contains fifteen species which are not included in that of Agardh. Of these, the majority are Australian forms, not previously recorded from New Zealand. In one or two cases I am by no means certain of the synonymy, so that this number may not be quite accurate. I attach a list of them to the end of this paper. Special mention should perhaps be made of Microcladia coulteri, as the genus is here recorded for the first time from the Australian region. I have for the last two years been aware of the existence of this genus in New Zealand, but have not announced it as I was not sure that our plant was specifically identical with the Californian M. coulteri (Harv.). If it be the same, the plant must be variable. I have specimens of this genus from Taylor's Mistake, and I have also received it from Dr. Chilton, of Port Chalmers, who obtained it at Long-beach, North Otago Heads.
Our list of New Zealand marine Algæ will now comprise 307 species, omitting the Protophyceæ. It is made up as follows: Agardh's list, 275; Corallines, 12; Harvey Gibson's list, 15; sundry; 5: total, 307.
Those marked “Sundry” include Griffithsia sonderiana (J. Ag.), Ceramium stichidiosum, (J. Ag.), Asparagopsis armata (Harv.), Landsburgia myricifolia (J. Ag.), Ulva bullosa (Roth.). Griffithsia sonderiana should probably replace G. setacea of Agardh's list; but I retain both for the present. The next three mentioned are probably accidental omissions from Agardh's list. Ulva bullosa appears in Hooker's Handbook, with a (?) attached, and no habitat is given. It is omitted altogether from Agardh's list. I have, however, specimens of what is doubtless Hooker's plant collected by Mr. T. Kirk, F.L.S., at Rocky Nook, near Sinclair Head, and by myself at Oriental Bay, Wellington. It must be remembered that the morphology of most of our species is not only known, but their fructification and internal structure have also been microscopically examined.* Of course, much still remains to be
[Footnote] * Nullam Florideam in systemate rite dispositam considerare decet, cujus structura interna et fructus nobis non sint omnibus numeria cogniti; neque certum judiciurn ferre licere de iis speciebus auctorum, quæ aut sterilea descriptæ vel delineatæ, aut analysibus frucfuura et structuræ erroneis aut deficientibus tantum cognitæ sunt. Quamobrem in hoc volumine, velut in antecedentibns, nullum speciem in textum adscivi, quam non ipse examinavi; species a me non visas aut in notis, aut inter species inquireridas, enumeravi. Paucissimas, facilius disttinctas, iconi tanturn fidens, hac auoctoritate adoptavi. (“Epicrisis Systematis Floridearum.” J. G. Agardh. Præfatio, pp. 1, 2.)
done; but I think we may assume that inmost cases the position of the species has been determined from its fundamental and not from its external characters.
Perhaps the first thing to be now noticed is the numerical proportions of the green, brown, and red seaweeds in our list. They are respectively 24, 55, and 228. “Now,” says Mr. G. Murray,* † “while in the arctic and Australian regions the Phæophyceæ far outnumber the Chlorophyceæ, in the tropical West Indian flora the proportion is very markedly reversed, and the green Algæ outnumber the olive-brown.” One would imagine at first, sight that this was due to the stronger illumination of the tropical seas; but Mr. Murray believes that the irruption of fresh water from the Orinoco and the tideless character of the Antilles are probably largely contributing agents to this result. Be this as it may, in New Zealand the Chlorophyceæ number, only 44 per cent, of the; Phæphyceæ; in the neighbourhood of Port Phillip the percentage increases to 65; for the Cape of Good Hope it is 71; and for the Indian Ocean it is 103: in Great Britain it is 68. There is here evidently a marked connection between the latitude and the percentages given. It may, of course, be objected that the area of the Port Phillip district is too small to compare with the others. I chose it because there are recent statisticst fed it, and thorough collections have been made from the locality. However, taking the most recent numbers for the whole of Australia,‡ the percentage is 55. This is probably too small, as many of the Chlorophyceæ are minute, and would escape notice unless very close search were made. It should also be remembered that the Algæ of southern are very much better known than those of northern Australia. On the other hand, it should be pointed out that the figures as given in the “Flora Antarctica” and in Dickie's list for Kerguelen Land§ show that in the antarctic district the numbers are about equal. This unexpected preponderance of green forms is to be accounted for, as will presently be seen, by the strange absence of the Fucaceæ from the antarctic flora.
Of course, the importance of these figures is in their bearing on the functions of the pigmentation of the Algæ and of plants in general, the-question at issue being, Does the chlorophyll act as a filter to allow only the useful rays of light to pass through, or is it an absorbing agent, collecting and utilizing
[Footnote] * Trans. Biol. Soc Liverpool, vol. v., p. 178.
[Footnote] †“Catalogue of Marine Algæ collected near Port Phillip Heads,” by J. Bracebridge Wilson, F.L.S. (“Proceedings of the Royal Society of Victoria,” vol. iv., part 2.)
[Footnote] ‡ “Journal of Botany,” July, 1893, p. 210.
[Footnote] § Phil. Trans. Roy. Soc., vol. olxviii.
those which are most serviceable to the plant in the decomposition of carbon-dioxide? The latter view has received the most support.* The same question may be asked in a slightly different form with regard to the phycoërythrin of the Florideæ and the phycophæin of the Phæophyceæ. Do these pigments act as a protection against the blue light of the sea, or do they absorb special rays, and give them out with altered wave-length, more suitable to the needs of the plant? It seems to me that in the present state of our knowledge discussion of the relative percentages in different districts of brown, red, and green seaweeds will help us but little to a solution of our difficulty, though perhaps the increase in the percentage of green seaweeds towards the tropics is easier of explanation by the theory of absorption and alteration of wave-length than by the theory, of protection. Data as to the depth to which species attain in different localities, and as to the variation of shade and tone with the depth, would probably be instructive.
It may be worth while to put on record here that I have observed in Champia noveæ-zealandiæ a remarkable iridescence, consisting chiefly of blue and green rays. When in the water the plant in this respect reminds one strongly of the brilliant iridescent elytra of certain beetles. On removing the specimen, from the water the iridescence to a large extent disappears, and there is not a sign of it after the plant has been dried. According to Kerner,† whose theories, if not always accurate, are frequently remarkable, and very often suggestive: “Several of the sea-inhabiting Florideæ, and sea-wracks belonging to the genera Phyllocladia, Polysiphonia, Wrangelia, and Cystoseira, even exhibit under the water a peculiar luminosity which may be compared with that of the luminous moss, although the optical apparatus is here essentially different. In the superficial cells of the luminous Phyllocladias are to be found plates segregated out of the protoplasm and closely adhering to the outer walls, which contain a large number of small, crowded lenticular bodies. From these minute lenses, the green and blue rays are chiefly reflected, and thus the peculiar iridescence is, produced. But, on the other hand, yellow and red rays are refracted on to the chlorophyll granules, and consequently these plates must be regarded as an apparatus for focussing the light, which, by its passage through the thick layers of water, has undergone a considerable diminution.”
It will be interesting to examine our Champia and see if any similar structure can be made out in it. I have not seen the original paper which is Kerner's authority for his statements. He also affirms in a short passage (loc. cit.) that may
[Footnote] * “Physiology of Plants,” p. 156: S. H. Vines.
[Footnote] † “The Natural History of Plants,” English translation, p. 388.
be worthy of quotation as new to most of my readers that, “If the barrel-shaped and spherical cell-structures connected into chains, the cyst-like and berry-shaped outgrowths of the unicellular Caulerpas and Halimedas … are accepted as contrivances by which light is collected and focussed on those places within the cells where chlorophyll bodies are heaped up, then no mistake will be made.” If there is any truth in this statement our Lychceæ darwinii and Caulerpa sedoides should serve excellently well to prove it.
The next point to which I must draw your attention is the proportion of species to the genus in our Algæ. As we have 307 species distributed among 117 genera, it is evident that we have just over two and a half species to the genus. According to Mr. G. Murray,* “In the warm Atlantic the genus averages well over five species; in the Indian Ocean the proportion is nearer four than three species to the genus; while at the Cape it is almost exactly three. This is instructive, when we remember, as I have elsewhere† pointed out, that, while the arctic Algæ average slightly more than two species to the genus, the West Indies and Australia average rather more than five. I estimate that the north temperate Atlantic yields an average of about four and a half species to the genus.”
Thus it appears we have only about half as many species to the genus as Australia has, but, as there are apparently only about three species to the genus at the Cape, it would probably be too venturesome to say that the small proportion in New Zealand is due to the fact that we are dealing with an insular rather than with a continental flora. It must be noted, however, that the Algæ of the Cape are probably not so well known as those of New Zealand. On the other hand, as our coastline is varied in character, and extends through more than ten degrees of latitude, we might have anticipated that those genera which have obtained a footing here would have developed many species, but this appears only to have been the ease in such genera as are variable elsewhere,—e.g., Polysiphonia, Gigartina, Delesseria, Cladophora.
This leads us up to the question of the distribution of our species. It may be as well to point out, for the help of the general reader, that marine Algæ are not so widely distributed as might on first thoughts be imagined. Indeed, it might be supposed that the only limitations to their distribution would be due to unsuitable environment; but this is by no means the case. In spite of the great geological age of this class, of plants, and their marine habitat, many of them are local in distribution. The deep sea is, generally speaking, a barrier,
[Footnote] * “Phycological Memoirs,” part ii., pp. 66, 67.
[Footnote] † Trans. Biol. Soc. Liverpool, vol. v., p. 77.
between them, and so are long reaches of sand and the mouths of large rivers. As I have been unable to find any observations on this matter in the books at my disposal, it would, perhaps, be as well to illustrate these statements from our New Zealand Algæ. Amongst other species endemic to the Chatham Islands is a very distinct form of Landsburgia, (L. myricifolia, J. Ag.). It is a fucoid several feet in length, and it must often, like L. quercifolia, be torn from the rocks by the waves; and yet, although it could almost certainly survive a lengthened tossing on the ocean's surface, it has been unable to establish itself on the mainland. It should, perhaps, be pointed out that after the hold of the rhizoid has been loosened, or when the plant—as generally happens with some species—is broken off above it, there is, probably, no possibility of its being able to affix itself again. At least, I do not remember having seen a plant that had evidently once been afloat re-establishing itself. It might, of course, although it had been subjected to weeks of tossing on the ocean's surface, go on producing spores, which might have a chance of germinating if the plant were finally cast up on a rocky shore. If a comparatively narrow arm of the sea can form a barrier to a strong, coarse plant like this, much more so will it be one to the delicate Rhodophycea. These plants soon bleach and disintegrate under the influence of the sun's light and heat when on the surface of the water, so that it is extremely improbable that the smaller forms could cross in a, living condition a wide arm of the ocean; and it is very improbable that even the larger forms could live for a lengthened time on the surface of the sea. Moreover, as we shall see presently, the facts of distribution do not by any means favour the supposition that ocean-currents do distribute living Algæ broadcast on the shores which they wash. It is still more difficult to imagine that oospores and carpospores apart from the plant should be able to cross successfully many miles of ocean.
I do not wish for a moment to deny that oceanic currents do sometimes determine the distribution of Algæ. The most notable example of this is perhaps to be seen in the case of Macrocystis, which follows the cold antarctic current up the western coast of South America, though not up the eastern side. Here, however, it is the temperature of the current, and not its direction, that determines the existence of the species. There is, however, a method by which even delicate species might in some cases be conveyed from shore to shore—that is, as epiphytes. Macrocystis, for example, apparently flourishes like the Sargasso weed in the open ocean.* If a plant
[Footnote] * “Flora Antarctica,” vol. ii., p. 465.
was torn from the coast-line, carrying with it many epiphytic species, it might remain an indefinite time in the ocean, breaking up under the influence of the waves, & c., growing and carrying with it a colony of delicate epiphytes, some of which might thus in the course of time be drifted on to the shores of other lands.
It is to be remembered that a seaweed having reached a new and suitable habitat has not necessarily to contend with species already occupying the coast. There is always plenty of room for it to live—plenty of unoccupied and suitable positions in rock-pools and in the neighbourhood of the tidal area. The flora of the sea does not clothe the rock-surface with a mantle as the herbage does the land. Every heavy gale with spring-tides tears hundreds of tons of Algæ from the rocks, leaving plenty of bare surface for newcomers or for germinating plants. What are the chief factors in the struggle for existence amongst marine plants I do not know; but it can scarcely be in the successful crowding-out of weaker competitors. Possibly the power of clinging successfully to the rocks is one of the chief of them; but, whatever they may be, we undoubtedly frequently find species restricted to a definite area.
In New Zealand we have many long stretches of sand and shingle that are practically marine deserts as far as the Algæ are concerned. Thus, on the west coast of the North Island, from Paikakariki northward to Taranaki Province, there is an unbroken barren beach. Now, in the neighbourhood of the Sugarloaves, at the New Plymouth Breakwater, the common form of Carpophyllum is the one figured as Sargassum phyllanthicm, pl. vii., “Atlas Botanique: Voyage de ‘l′ Astrolabe.’” This plant, however, is quite distinct from the true Carpophyllum phyllanthum, and is either a neglected species or a strongly marked variety of C. maschalocarpum. From Paikakariki southward the ordinary form of C. maschalocarpum, together with C. phyllanthum, is common; and on this portion of the coast I have only found the New Plymouth form on rare occasions in drift-weed on the beach at Ohiro Bay, whither it may have come with the current from Taranaki. Thus a sandy track here separates two distinct and practically discontinuous varieties. Climate, which, of course, is the main agent in determining distribution along a continuous coast-line, can scarcely be said to play a part here, much less in the case of Lessonia varieyata (J. Ag.). This is abundant in deep tidal pools near Wellington Heads, and it extends along the coast to some little distance past Cape Terawhiti, when it disappears, although the coast-line continues of the same character northward as far as Pukerua. Its place is partially taken by Ecklonia. Here it is extremely difficult to account for the local distribution.
Not much, however, is at present known about the internal distribution of our species. As the islands stretch through ten degrees of latitude there is sufficient difference of temperature to cause considerable differences in the marine flora. Many of our species are principally or exclusively northern in their distribution, others are only found in the southern portion of the Islands. Of course, many plants which are at present known from restricted habitats in New Zealand will doubtless be found to be widely distributed. I have already a considerable list of new localities, but I will leave it for some future occasion, as I do not wish to burden this paper with it, nor do I intend to discuss further the distribution of our species within New Zealand.
There now remains to discuss the external distribution of our Algæ, which is of considerable interest. It should first be pointed out that no important order is wanting in our list, though several of the smaller ones appear to have no representative here. The small order, Squamariea, which is found throughout the Atlantic, in the Indian Ocean, at the West Indies and the Cape, and in Australia, is probably the most considerable of these. Our genera, too, as might be expected in such an ancient division of plants, are, as a whole, very widely distributed. It is, of course, to be expected that they should be-most closely allied to those of the corresponding latitude in Australia, and this is the case. In south-eastern Australia there are about 180 genera, in New Zealand about 116. Of these, eighty-nine are common to both districts. The warm Atlantic and the Gape have eighty-five genera, and the Indian Ocean and the Cape eighty-six genera in common (G. Murray, loc. cit.). Of course, the percentages in each case show greater differences, but it will be seen that the large proportion of genera common to New Zealand and south-eastern Australia is not necessarily any proof of the close affinities of the floras. We have, for example, more than fifty genera in common with a district so remote and so different in climatieal conditions as the West Indies. On the other hand, there are only eight genera confined to Australia and New Zealand—viz., Hormosira, Xiphophora, Cystophora, Notheia—amongst the Fucacea; and four genera in the Rhodophycea, all belonging to the order Spharococcoidea—viz., Curdicaa, Melanthalia, Sarccladia, and Dicranema—but, of these, Sarcocladia consists of only two species—one belonging to Western Australia, and the other, a New Zealand one, only very doubtfully placed in the genus by Agardh. There is also a very doubtful species of Dicranema from the Red Sea. Such well-defined and distinctive genera as Hormosira, Xiphophora, Cystophora, and Notheia, however, prove a distinct connection between our
Fucacea and those of Australia. Indeed, the distribution of the nine genera of this order found in New Zealand is sufficiently remarkable to be summarised here. Five are confined to New Zealand and Australia, two are endemic to New Zealand. One is tropical in distribution; and the last—D'Urvillæa—is clearly antarctic, being confined to New Zealand, the Falklands, Cape Horn, and Kerguelen's Land; but even this is represented in Australia by the closely-allied and scarcely generically distinct Sarcophycus. Our twoendemic genera are also Australian in their relationships. Landsburgia finds its closest ally in the genus Phyllospora, which is represented in Australia, and Marginaria coinesnearest to Scytothalia of Western Australia and Tasmania. This last genus,-however, is probably to be regarded as antarctic rather than Australasian, for there is a species. (S. obscura, Dickie) in Heard Island, and another (S. jacquinotii, Mont.) in South Shetland. Harvey and Hooker comment on the last-mentioned plant in a noteworthy passage, part of which I shall quote, as it bears on the present discussion:—
“Scytothalia jacquinotii. Hab. Graham's Land, 63° S.; Deception Islands; South Shetlands.
“The existence of this seaweed on the icy shores of an antarctic land, in the longitude of Cape Horn, is a most singular and anomalous fact, for I believe it to be the only species of the tribe which inhabits the colder or antarctic seas of South America.”*
Again, p. 457: “No such obstacle [i.e., difference of temperature] prevents the fullest interchange of Cystoseirée between New Zealand and the temperate seas of South America. It however is the fact that, whilst this group literally abounds in certain latitudes and longitaides, which are those of New Holland and the west Pacific, they are nearly absent from analogous positions in the longitude of South America.”
I may add to this that the “Challenger” Expedition has shown they are also absent from the antarctic islands.
To sum up, then, six of the New Zealand genera of Fucaceé are found in Australia, and four of them are confined to the two regions, whilst a fifth, Carpophyllum, is only represented elsewhere by a single species—i.e., G. scalare—at the Cape. The remaining three are allied to Australian forms; but two of them are also antarctic in distribution. On turning to the New Zealand species belonging to these genera we find that, out of twenty-one, ten are confined to Australia
[Footnote] * “Flora Antarctica,” vol. ii, p. 456.
and New Zealand, one is antarctic, and ten are endemic. Here, again, we have a clear illustration of the Australian connection.
But this connection must not be exaggerated. A reference to a different' district will be useful to us here. Seventy – seven per cent, of our genera are found in Austratic; 60 per cent, of the Cape genera are also found in the Atlantic and Indian Oceans. From an estimate of this crude description, it appears that as far as ratios go our connection with Australia is rather closer than that of the Cape with the East Indies or the warm Atlantic; but it must be remembered that the Algæ of Australia are highly characteristic, and, whereas in New Zealand we have only nine endemic genera—viz., Marginaria, Landsburgia, Scytothamnis, Chladymenia, Apophloé, Æodes, Ectophora, Abroteia, Pandorea—there are in the neighbourhood of Port Phillip alone representatives of about fifty genera confined to Australia, or, while 8 per cent, of our genera are endemic, about 28 per cent, of those found in south-eastern Australia are exclusively Australian. Thus, while our marine flora, has marked affinities with that of Australia, there are also marked differences between them, many of the most distinctive and prominent Australian genera being unrepresented here. This, of course, only confirms what we know of the origin of our flora-from the evidence of the flowering plants and ferns.
But the study of percentages, whilst giving an appearance of reliability, is very apt to be deceptive, and more striking and reliable information is sometimes to be obtained from the examination of limited groups. We have already seen that our Fucaceæ are largely Australian, and before passing' on to the examination of the distribution of our species I must call attention to the distribution of the New Zealand genera of the order Laminarieæ. Our representatives of this order have undoubtedly an antarctic facies. They are five in number—viz., Adenocystis, Ecklonia, Lessonia, Macrocystis, and Chorda. Of these, Adenocystis and Lessonia are antarctic in their distribution; Macrocystis and Ecklonia, though not exclusively antarctic, reach their greatest development in the colder southern seas. The genus Chorda is represented by one species here—G. lomentaria, said to be found in Tasmania, Falkland Islands, North Atlantic and Pacific Oceans. I doubt, however, whether the southern plant is specifically identical with that of the Northern Hemisphere. That our Fucacea should be mostly Australian, but the Laminarieæ largely antarctic, is a remarkable fact, which I shall not attempt to explain.
It remains now to consider the distribution of our species. In these our shores are comparatively poor. We have only
307, as against 474* in Great Britain (excluding in both case the Cyanophyceæ). Of course, the difference is to be attributed in part to the greater completeness of the British list. Australia, our nearest neighbour, is, on the other hand, remarkably rich, in its marine flora. Mr. Bracebridge Wilson has collected at Port Phillip Heads and its neighbourhood no less than five hundred species of Algæ—a remarkably rich harvest from one district. When we remember whaat a long and varied coast-line New Zealand possesses we may, I think, reasonably say that further search will probably considerably enrich our flora. No collections have been made in the West Coast Sounds since the tune of Hooker's Handbook. Dredging there would probably reveal a few, perhaps many, species of Florideæ. Remembering the imperfections of our list, we may roughly classify our species as follows:—
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|Endemic to New Zealand||162|
|Endemic to New Zealand and Australia||46|
|Widely distributed over northern and southern seas||47|
|Confined to southern, or to southern and warmer seas||21|
I think that this list, however crude as a representation of actual facts, will be found to be accurate as far as our present knowledge goes. It, however, requires a little explanation. The definition of “antarctic” adopted is that given in the “Flora Antarctica,” vol. ii., p. 210, et seq. In the case of two or three species out of the thirty-one, its application may be doubtful; but that it is correctly applied in the remaining cases will be clearly seen shortly. Of the twenty species included under the heading “Confined to-southern, or to southern and warmer seas,” some four or five seem to be confined to New Zealandt Australia, and South Africa; nearly all the others extend northwards into the tropics; one or two perhaps should be considered as antarctic, but they are widely distributed.
From the above table it will be seen that about 53 percent, of the known New Zealand species are endemic. It might have been supposed that in such an old division of plantlife specific stability would obtain through a considerable length of time, geologically, speaking, but this is manifestly not the case. The fact that we have such a large proportion of endemic species shows that here as well as elsewhere there has been among the marine Algæ considerable development in comparatively recent geological times. We have, moreover, a considerable number of variable species; but here it is difficult to say how far the variations are due to the direct action of the environment during the life of the individual, or to more
[Footnote] * Revised List of British Marine Algæ, by Holmes and Batters.
subtle inherited tendencies. Such a variety as Hormosira sieberi, some bleached forms of Cystophora, and a certain variety of Jania, micrarthrodia, are due to the plants living in pools that can only be reached by the highest spring-tides. Situations and external circumstances likely to modify the normal form of th plant should always be noted in collecting varieties.
It is rather remarkable that while we have so many endemic species so few of the remainder should be exclusively Australasian. We have already seen that about a fourth of these belong to the Fucaceæ, the remaining three-fourths are Floridean. The green seaweeds are apparently too widely distributed to show any distinct kinship between the two districts. Future observers should remember that we may have from time to time adventitious additions to the Australian element in our flora. In these days of copper-painted and copper-sheathed ship-bottoms it is perhaps hardly likely that ordinary traders will bear across the Tasman Sea many living Algæ attached to their sides; but I have known several instances where hulks have lain long in some Australian port and then been brought across to New Zealand to do service here. Such vessels, if undocked preparatory to the journey, would bring across with them many living specimens of Australian animal and vegetable life.
The most interesting element amongst our marine Algæ is undoubtedly the antarctic, which may be again subdivided as follows:—
|New Zealand antarctic, Tasmania (sometimes Australia)||12|
|New Zealand, South America, and antarctic islands||8|
|New Zealand and antarctic South America||6|
|New Zealand and antarctic islands||5|
As these results are of some importance I attach, a complete list of these species, giving details of the external distribution. Now, it is to be noted that no less than 10 per cent, of our species are antarctic in distribution; of these, a half, or 50 per cent., are found in Kerguelen, and about the same percentage (twenty species) of South African Algæ are also found there; and this notwithstanding that South Africa is separated from Kerguelen by only 50 degrees of longitude and New Zealand is separated from it by about 150 degrees. Moreover, it will be seen from the detailed list that no plant is common to the three regions.
Again, seven plants occur in New Zealand, the antarctic, and Tasmania, but not on the mainland of Australia. One or two of them, of course, may yet be found in Victoria; but several of them are so conspicuous that they could not be
overlooked even by a casual observer, so that their non-existence in southern Australia may be regarded as proved. Such are Adenocystis lessonii, Lychæste darwinii, and Nitophyllum multinerve. Why should these plants be found at such widely intervening points, but not have crossed Bass Strait? Why, again, should five plants be confined to New Zealand and the antarctic islands? And, lastly, why should only two of the thirty-one reach South Africa?
Of course, no matter what explanation be accepted, there will always be difficulties and anomalies in the way of its eomplete adoption. For example, Codium adharens has generally been regarded as a plant belonging to warmer seas. It just reaches the south coast of England, and the coldness of the waters of the Atlantic was believed to prevent it from spreading north ward. However, it occurs plentifully in New Zealand,- and the “Challenger” has shown that it is also found at Kerguelen. Nevertheless it is wanting both at the Cape and Australia. The genus Microcladia occurs on the coasts of the Atlantic, California, New Zealand, and Kerguelen. As the species are small, it may, however, be yet found in the intervening positions.
There are at least six possible solutions of our difficulties: (1) Further knowledge may fill in gaps at present existing, and reduce apparent anomalies; (2) dispersal may have taken place by other methods than those already referred to; or the present distribution may be due—(3) to existing, or previously existing, ocean-currents, (4) to the partial extinction of species once widely spread, (5) to the former greater extension of land-surface in the southern oceans, or (6) to some combination of some or all of these causes.
From what has already been said it will be clear that the first hypothesis is quite inadequate to solve our difficulties. In other branches of botany the reconciliation of opposing statements has frequently been attained to by a more careful attention to synonymy; but it should be pointed out that Agardh and Harvey are practically our sole authorities for Australia and New Zealand, so that there is here likely to be but little confusion owing to varying estimates of specific and generic differences. In the other districts referred to the naming of the species has been carried out with the greatest care by recent investigators. Contrasts may be lessened in some cases by further investigation, but resemblances are much more likely to be strengthened than diminished; and many species are so distinct and so abundant where they do occur that the negative evidence of their omission from a list must be regarded as satisfactory proof that they do not occur in the district.
The second conjecture need not detain us long. The only
other method of distribution besides those already referred to that occurs to me as being worthy of mention is that by means of sea-birds.
It is by the agency of these that Sir Joseph Hooker endeavours to account for the existence of the phanerogamic flora of Kerguelen's Land,* but it is practically hopeless to account for the distribution of our seaweeds by any such method. Many of them live below low-tide mark, and so would scarcely be likely to be picked up by birds except as drift-weed. Some of these with anomalous distribution are extremely delicate and very small—e.g., Polysiphonia ceratoclada, which grows to a length of 15mm. or 20mm., and is less than 1mm. in diameter. It is, however, a very distinct and recognizable species. It is common in New Zealand, and has been reported from Amsterdam and St. Paul Islands. Such a distribution could scarcely have been effected by sea-birds. Still, this is a single extreme case, and of itself does not disprove or prove anything. It is merely to be taken as a typical example of the difficulties to be met with, and is only to be regarded in conjunction with other facts. If, again, sea-birds have been distributing-agents, why should they have carried so many Fuegian and New Zealand forms bo Kerguelen and Tasmania, but not to South Africa and southern Australia? Whatever may have been their work in distributing landplants, I think that they may have been practically left out of consideration as distributors of the Algæ. If this is so, then the discussion is somewhat narrowed down; and it may be possible to get from the Algæ more definite evidence upon various questions of distribution than is obtainable from the flowering plants.
We have now to refer to the action of ocean-currents. I have already shown that in many cases these have been unable to establish a species on the further side of a comparatively narrow ocean – barrier, even when similar conditions appear to exist in both localities. Sir J. Hooker, however (loc. cit.), states that “oceanic currents have doubtless brought the marine Algæ to Kerguelen Land.” This may be true for the majority of them, but I cannot think that it is true for all. For example, under this hypothesis, why should Adenocystis lessonii, Polysiphonia abscissa, Nitophyllum multinerve, and several other species have drifted from Fuegia to Kerguelen, but not from Tasmania to Australia? or how did Calophyllis hombroniana, Antithamnion ptilota, and two or three other species reach the antarctic islands from New Zealand without establishing themselves at intermediate points? Whatever may have been the centre of distribution, we cannot account
[Footnote] * Phil. Trans. Roy. Soc., vol. clxviii., p. 13.
for these facts by the action of oceanic currents alone, even if in past time they were different in direction from those at present existing. Moreover, the distribution of the Fucaceæ and the Lainarieæ gives a character to the antarctic Algæ that seems to denote something more than dispersal from a common centre.
However, a full discussïon of this question would involve an investigation into the distribution of the seaweeds throughout the southern ocean, and would lead me quite outside of the scope of this paper. We have in ocean-currents no doubt a vera causa, but what the limits of its action are would be a very difficult matter to determine. The generally westerly drift in the forties will no doubt go far to explain some of our difficulties. It may possibly account for the presence of some Fuegian forms in Tasmania and New Zealand, but not in Australia; and the trend of this current at the south of the Cape may explain the absence of Fuegian plants there. In speaking of D'Urvillæza utilis, Hooker says, “Though carried by the currents along the ocean to the south of the Cape of Good Hope (for it was collected in that meridian in the 51st degree, floating in the open ocean), it does not appear to inhabit or be cast upon the southern extremity of Africa.”* Such statements as these, in the absence of knowledge as to the age of the species and of oceanic currents, can only be looked upon as conjectures; but, making every allowance for their possible truth, there is still, I think, presumptive evidence in the facts already given that other causes have been at work in determining the present distribution of the Algæ in southern oceanic islands.
Whether species at present discontinuous may at one time have been widespread we are not likely to be able to determine, nor can we consider this as a means of explanation until extraneous evidence has been brought forward to show that areas at present widely separated were more closely connected in the past. Such evidence is not altogether wanting. The theories of Mr. A. R. Wallace† and Captain Hutton‡ are well known here, and I need scarcely refer to them further; but I should like to quote a short passage that may not be so well known to New Zealand readers, from the “Botany of the ‘Challenger’”§
“The now complete botanical researches for the present work have brought to light some interesting facts, confirming generally the views enunciated by Darwin, Hooker, and
[Footnote] * “Flora Antarctica,” vol. ii., p. 455.
[Footnote] † “Island Life,” 2nd ed., chap. xxii.
[Footnote] ‡ “New Zealand Journal of Science,” vol. ii., p. 1: “Origin, of the New Zealand Fauna and Flora.”
[Footnote] § “Botany of the ‘Challenger,’” vol. i., pp. 4, 5.
Wallace, and more fully set forth by Wallace in the book under consideration [i.e., ‘Island Life’]. There is, however, one important exception. All Wallace's speculations on former land-connections are based upon the present relative depths of the intervening seas, and, while admitting, or rather suggesting, a former land-connection between New Zealand and eastern Australia, he utterly rejects Captain Hutton's theory of a southern continent uniting the former with South America, and perhaps also with South Africa. Without going as far as Hutton, we think the botanical evidence, as explained further on, strongly favours a former greater landconnection in a lower latitude in the south temperate zone than Wallace admits, and we cling to ‘this forlorn hope of the botanical geographer,’ as Sir Joseph Hooker terms it, for all the various means by which plants are diffused seem to be inadequate to account for the present distribution of plants in the coldest southern zone of vegetation.”
Again, Mr. Botting Hemsley, commenting on the lanplants of Kerguelen,* says',—
“Numerically, then, there is a preponderance of Fuegian forms represented in Kerguelen and the other islands under consideration as to what may be termed New Zealand forms. The antarctic flora may have spread from America; but with all the facts before us there does not seem to be a special affinity between the floras of Kerguelen, & c., and Fuegia, as distinguished from the flora of the zone generally. Taking the New Zealand flora as a whole and the Fuegian flora as a whole, the former is as strongly represented in these islands by the same and allied species as the latter, indicating a former flora of the same elements spread all round a southern zone, which included a part of New Zealand and the extreme south of America, as well as the present isolated spots of dry land in the same latitude.”
The statements here are based on the evidence derived from only twenty-seven flowering plants and ferns. On turning to our Algæ we find that the statements made above are on the whole confirmed by them. There are twenty-two species occurring in New Zealand and the antarctic islands, and twenty-five in New Zealand and South America and the neighbouring islands. Six are confined to New Zealand and South America, five are confined to New Zealand and the antarctic islands. Now, seventy-one species of marine Algæ are known from Kerguelen, and about 110 (neglecting Protophycece) from South America. Thus the two elements are represented here in about equal proportions, although the antarctic-island forms perhaps preponderate a little. It is, how-
[Footnote] * “Botany of the ‘Challenger,’” vol. i., p. 253.
ever, to be remembered that we have probably excluded some antarctic species of the Campbell and Auckland Islands not found on the mainland of New Zealand. There is reason to believe that a thorough search of these islands would add considerably to our list of antarctic Algæ.
As a result of our whole investigation, I think that we may now fairly say that the examination of our Algæ has confirmed, and perhaps to a slight extent strengthened, the general results obtained by those who have similarly studied the flowering plants.