In this paper it is intended to briefly delineate the Flora of the immediate vicinity of Auckland, so far as regards the Phænogams and higher orders of Acrogens. The lower Acrogens and the Thallogens will, it is hoped, form the subject of a subsequent paper.
The district is divided by the Waitemata into two parts, the well known Isthmus of Auckland, comprising the City of Auckland, with the towns of Onehunga and Panmure, and Takapuna, or the North Shore, which includes the site of the pretty town of Devonport.
The Isthmus of Auckland comprises an area of about 30,000 acres, its extreme length being about eleven miles, from the Whau Creek to the Tamaki, and its extreme width rather more than six miles. On the north, east, and west, it is bounded by the Waitemata, the Tamaki Creek, and Whau Creek, with the exception of a portage, less than two miles in length, from the Whau Creek to Motu Karaka on the Manukau; and the still shorter portage between Halswell's Creek on the Tamaki, and Fairburn's Creek on the Manukau. On the west, it is bounded by the Manukau from Motu Karaka to Fairburn's Creek, a distance of ten miles, not making allowance for the indentations of the shore. Thus, with the exception of about three miles, it is bounded by water.
The Takapuna District comprises that part of the North Shore extending from the North Head of the Waitemata to Lucas' Creek, and from the head of Lucas' Creek to Omangia Bay on the outer coast. It is roughly triangular in shape, and, with the exception of less than six miles from the head of the creek to Omangia Bay, is bounded by the sea. Its area is about 13,000 acres.
The entire area thus comprises about 43,000 acres, no part of which is more than eight miles in a direct line from Queen-street wharf.
Both districts belong to the tertiary formation, and are composed of stiff clays, marls, and sandstones. On the Isthmus this has been pierced by numerous volcanoes, the lava streams and ashes from which cover fully two-fifths of its area, affording a soil of great fertility. Amongst the lava streams are considerable depressions, which, from the drainage becoming obstructed, form extensive swamps, in some cases dried up during the summer. The hills are volcanic cones, of low elevation, the highest being Mount Eden, which is only 642 feet above the sea level. In the Takapuna District volcanic action has been confined to the North Head, Mount Victoria, the western shore of Shoal Bay. The Pupuke Lake fills the bed of a crater about two-thirds of a mile in diameter, and has a depth of twenty-eight fathoms. The highest point is Mount Victoria, which is under 300 feet.
Nearly the whole of the Isthmus has been brought under cultivation,* although here and there patches of clay land, or unusually rough portions of a lava stream, yield merely a sparse return of native grasses, with a large number of introduced plants; these are, however, rapidly decreasing, and from the almost entire destruction of the clumps of bush that formerly clothed the gullies, and the scrub that concealed the ruggedness of the scoria, indigenous
[Footnote] * The population of the Isthmus is about 23,000.
plants exist even under less favourable circumstances than in an agricultural county in England, for the friendly shelter of hedge-rows and patches of coppice is almost unknown. In the Takapuna section, the unreclaimed clay lands have been so frequently fired, that the natural vegetation over large areas is restricted to stunted tea-tree and similar small shrubs, with a few grasses and introduced plants, the soil itself becoming deteriorated in an increasing ratio with each successive burning.
The scoria cones of the Isthmus have become covered with a dense sward of introduced grasses and small forage plants, amongst which a few native plants, as Carex breviculmis, Ranunculus australis, Danthonia semi-annularis, and others, still maintain their existence; in rough places, if at all sheltered, Doodia caudata, Adiantum œthiopicum, and A. hispidulum, are usually found, and appear to flourish with as great vigour as when on the stiff clays. Another interesting fern, Gymnogramme leptophylla, is occasionally observed on bare places, but from its small size is easily overlooked. Scleranthus biflorus forms patches amongst the introduced grasses, varied by occasional masses of Acœna sanguisorbœ and A. Novœ Zelandiœ, contrasted with solitary plants of Vittadinia australis. Numerous ferns and low-growing plants are found amongst the blocks of scoria which form the lava fields in all directions, and, where the shrubs and small trees have been preserved, these exhibit a luxuriance of growth for which one is altogether unprepared. Polypodium Cunninghamii frequently produces fronds over twelve inches in length, Hymenophyllum Javanicum, and Trichomanes humile, are often found in the most luxuriant state. The same remark applies, in an equal degree, to the shrubs and trees found in these seemingly unfavourable habitats; Tetranthera calicaris, Griselinia lucida, Brachyglottis repanda, Alectryon excelsum, Panax Lessoni, are abundant, and attain their usual stature and bulk. This luxuriance of growth in such an unpromising locality is a striking proof of the great amount of moisture in the atmosphere of the district. Taking 100 to represent saturation, the mean for Auckland is found to be 75; only two localities in the colony are known to give higher means, viz., Taranaki and Hokitika, for which the figures are respectively 80 and 90.
Astelia Solandri occurs frequently on the rocks, and is usually accompanied by by Peperomia Urvilleana; more rarely, Astelia Banksii is found in similar situations. Cheilanthes Sieberi and Nothochlœna distans are abundant upon exposed rocks, as are Pellœa falcata and P. rotundifolia in sheltered rocky places; while Asplenium flabellifolium in many localities lines every crevice with a drapery of the tenderest green.
The undulating clay hills and gullies are mostly clothed with low-growing tea-tree and Pomaderris ericifolia, varied by clumps of fastigiate Dracophyllum squarrosum. Cordyline Pumilio, Lycopodium densum, and Phylloglossum Drummondii are to be found in all suitable localities, and in wet places,
Drosera binata, Lycopodium laterale, and Gleichenia hecistophylla are abundant; the lower parts of the gullies are usually swamps filled with raupo, and edged with a varied growth of sedges and other uliginal plants, amongst which Isachne australis often occurs in abundance; the slopes are often clothed with low scrub, chiefly composed of the commoner heathworts, Coprosma lucida, Cordyline Banksii, etc.
Conspicuous in the patches of bush still remaining are Tetranthera calicaris, Vitex littoralis, Metrosideros robusta, Nesodaphne Tawa, N. Tarairi, Leptospermum ericoides, Myrsine salicina, M. australis, Persoonia Toro, Knightia excelsa, Elœocarpus dentatus, Hedycaria dentata, Dammara australis, with many other fine species, accompanied by the chief characteristic undergrowth of the northern forest, Alseuosmia macrophylla, Coprosma grandifolia, etc., and many small ferns. Astelia Solandri, Pittosporum cornifolium, Dendrobium Cunninghamii, Earina mucronata, and E. autumnalis are commonly epiphytic on the larger trees, Tmesipteris Forsteri is epiphytic on the stems of Cyathea medullaris, C. dealbata, and Dicksonia squarrosa.
On the coast the pohutukawa is still common, although all specimens sufficiently large for the purposes of the ship-builder have long since been removed, except at the Pupuke Lake, where some noble examples are yet to be seen. Astelia Banksii is abundant in sheltered places on the cliffs, and, in some localities, the renga-renga (Arthropodium cirrhatum), makes a fine display. Crantzia lineata, Paspalum distichum, Triglochin triandrum, Chenopodium ambiguum, and Salicornia indica are common in salt marshes and mud flats, whilst most of the ordinary littoral plants may be found in the varied habitats afforded by a coast line of fully sixty miles, making due allowance for the indentations and windings of the shore.
The chief localities for plants of special interest are Waiatarua or St. John's Lake, the lava field near Mount Wellington, etc., the head of the Manukau, the Onehunga Springs, the Bishop's Creek, Coxe's Creek, etc., on the Isthmus; in the Takapuna section, the North Head, Pupuke Lake, and the deep gullies near Stokes' Point.
A few species appear to reach their ultimate range of distribution in this small area :—Pomaderris elliptica attains its southern limit at the Whau and Lucas' Creeks; Acœna Novœ Zelandiœ, Corysanthes Cheesemanii, Astelia Hookeriana, have not yet been observed south of the Tamaki; nor has Phylloglossum Drummondii.
Viola Lyallii, Potentilla anserina, Myosotis Forsteri, and Carex inversa apparently find here their northern limits, and are remarkably local.
The effects of the changed conditions of plant life incidental to agricultural progress, are chiefly exhibited in two directions,—(1.) the restriction of species once plentiful in the district, to narrow habitats, in some cases to a few individuals only, and conversely in the increase of a limited number of species;—
(2.) in the rapid diffusion of many introduced plants, followed under certain circumstances by a further displacement of indigenous forms. Contrary to popular belief, there is no evidence to show that the operations of the settler have entirely eradicated even a single species; although many forms once common in the district have become extremely local, and exist under widely altered conditions. This conclusion is not invalidated by the absence of several species,—Colobanthus Billardieri, Spergularia marina, Plagianthus betulinus, Panax Edgerleyi, Griselinia littoralis, Loranthus tetrapetalus, Olearia albida, Celmisia longifolia, Ozothœmnus glomeratus, Sapota costata, Veronica macro- carpa, V. parviflora, Aspidium coriaceum; for although on various grounds they might reasonably be expected to occur in the district, they are, with one or two exceptions, also absent from wide adjacent areas both to the north and south. This conclusion is further supported by the fact, that notwithstanding the sameness of the conditions under which vegetation exists in this district, it yet affords a larger number of indigenous species than any similar area which has yet been examined.*
Although the Flora now under consideration is that of a very limited area, and has had the conditions of plant-life greatly modified, it may fairly be taken as representative of the Flora of the colony, and pre-eminently of that of the Northern Island, excepting in both cases the alpine and sub-alpine sections. More than 200 of the plants now enumerated are common to the extreme north and the extreme south, 350 are common to both islands, and rather less than 100 species are peculiar to the North Island. No species is absolutely circumscribed within its limits, although several of its members are extremely local. Compared with the number of Phænogams and Ferns comprised in the New Zealand Flora, its members are in the proportion of 1 to 2.8; separately, the Phænogams as 1 to 2.7, the Ferns and Fern allies 1 to 1.7. The number of species known to occur in an indigenous condition in the Province of Auckland is upwards of 800, of which considerably more than half may be collected in the immediate vicinity of its capital.
A comparison of the Floras of the chief centres of settlement in the colony would afford results at once interesting and instructive, but the materials for making a comparison of this kind have not yet been prepared. It is, however, highly probable that the Flora of the immediate vicinity of Wellington will prove even more typically representative of that of the entire colony, although less purely characteristic of the North Island. It may be expected to exhibit a somewhat larger number of Ferns, with a smaller number of Phænogams.
[Footnote] * Compare Buchanan's Lists of Plants found in the Province of Marlborough, and in the Vicinity of Mount Egmont; Lindsay's Contributions to New Zealand Botany; “The Botany of the Great Barrier,”—Trans. N. Z. Inst., Vol. i.; “The Botany of the Thames Gold Field,” “The Vegetation of the Neighbourhood of Christchurch,” and “A List of Plants found in the Northern Part of the Province of Auckland,”—Transactions, Vol. ii.
On the other hand, the Floras of Christchurch and Dunedin will probably prove of a more local type, less rich in the number of species and especially deficient in the higher Acrogens.
In the following catalogue, the numerals prefixed are intended to represent the relative abundance of each species. The series employed is 1, 2, 3, 4, 5, 10, 15, 20. The first three are restricted to local species, represented by a few individuals, as Spiranthes australis; 4 and 5 are used for local species, represented by a larger number of individuals, as Corokia buddleoides. But it must be borne in mind that the varying conditions of vegetable life incident to a populated district, are constantly modifying the relative frequency of indigenous species.