Art. XXVI.—On the Naturalized Plants of the New Zealand, especially with regard to those occurring in the Province of Auckland. *
[Read before the Auckland Institute, November 15, 1869.]
In the present imperfect knowledge of the laws which regulate the distribution of species, any authenticated records of the introduction of exotic species into new countries, and their subsequent diffusion, must of necessity possess high value, and be alike calculated to throw light on the obscure past, and to prevent the adoption of error in the future. the opportunities afforded by modern colonization, or watching the introduction of foreign species, and noting their diffusion in new countries, by agencies uncontrolled by man, have been, to a great extent, neglected. In truth, it is far easier to recognize results, than to watch the processes by which the results are brought about; a few years sometimes suffice to show us the displacement of the greater portion of the vegetation of certain localities, although the process itself has been so gradual as almost to have escaped notice; yet when, as in these islands where settlement is in its infancy, we find much of the original vegetation displaced by non-indigenous plants, established about the early mission stations, and seats of commerce, about mines, timber stations, and cattle runs, in short, wherever the immigrant has fixed his temporary or permanent home; we are insensibly led to entertain wider views of the changes which the floras of countries of ancient civilization must have undergone by successive immigrations of plants from other countries. In this light we may glance for a moment at the flora of the British Islands, the flowering section of which is supposed by botanists to consist of naturalized plants to the extent of from one-seventh to one-fourth, or even a higher proportion. If we look back to the time of Phoenician commerce and settlement in the western part of the island, we can readily conceive of plants, from the countries on the Euxine and the Mediterranean, having been accidentally introduced and amalgamated with the indigenous flora. In later times we have no difficulty in extending the idea to those countries which sent to Britain successive hordes of invaders; and in the present day we can point to plants and animals, alike of accidental introduction in the footsteps of commerce, which have become widely naturalized; take for examples, Impatiens fulva, Elodea alsinastrum, and the fluviatile mollusk Dreissena plymorpha.
Now although the robust growth of the modern civilization has buried many traces of the less vigorous ancient forms, it would seem not utterly impossible that a more careful and comparative examination than has yet been made of the floras of the countries, from which Britain received her ancient settlers and invaders, might lead to the removal of much of the uncertainty and doubt that exist as to the indigenous or exotic origin of so large a proportion of her flora; and might also show, to some extent, what those countries had received from Britain, and from each other. To apply this in
[Footnote] * On the subject of Introduced Plants in New Zealand, see Paper by Dr. Hooker, F. R. S., and W. Locke Travers, F. L. S., in “Natural History Review,” Vol. iv., pp. 123 and 617, 1864.—
the case of New Zealand: it is but a century since the islands were discovered by Cook; less than sixty years since the early visits of whalers, and the establishment of the first mission stations; and not half that period has elapsed since settlement was commenced in a systematic manner, yet already the number of naturalized plants,—that is to say, of non-indigenous plants propagating their species, and becoming diffused without the intentional agency of man, or even in opposition thereto, in the Province of Auckland alone,—is equivalent to fully thirty per cent. of the entire number of flowering plants found within the limits of the Colony; a proportion equalling, as we have already seen, that which exists in the British Islands, with a commerce dating from a period anterior to the Christian era. Some of these introductions have largely displaced the original vegetation in many localities, from the North Cape to the Bluff; from the sea level to the highest spots on the hills trodden by the miner or shepherd; while others are confined to a limited area, and apparently exercise no direct influence on the original flora.
A reliable account of the present state of even a few species is a contribution of no small value, tending to prevent the uncertainty and confusion with regard to the geographic origin of a large portion of the flora, which we have seen to prevail so largely in countries of old commerce and civilization, affording a starting point for measuring the rate of diffusion, and noting the power of displacement of, or amalgamation with, the original flora; and in this and other points preparing important material for unlocking the histories of past immigrations in other countries.
The object of this paper is simply to place upon record the present state of the diffusion of naturalized plants in this province, as fully as the available material will allow, with a due regard to conciseness. In those cases where the species under notice is known to occur in other parts of the colony, the facts will be mentioned, but unhappily, these are far too few to admit of this sketch being considered anything more than a sketch of the naturalized plants of the Province of Auckland.
For the facts recorded in this paper, the writer is personally responsible, except when otherwise stated; the only published accounts available, are a list of about sixty species given in “Flora Novæ Zelandiæ,” Vol. ii.; a list of about one hundred and seventy species in the “Handbook of the New Zealand Flora,”—the additions comprised in which, were largely contributed by the present writer; and lists of the naturalized plants of the Great Barrier Island, and other localities, prepared by him, and published in the “Transactions of the New Zealand Institute,” Vol. i.
Many important bearings of this subject will, it is hoped, afford material for future study. The increased diffusion of certain of the indigenous species by external agencies, only called into operation since the settlement of the colony; the possible introduction of a few additions to the original flora, by the Maori race; the displacement of a portion of the original species; the spontaneous amalgamation of introduced and native species for the benefit of man; the relative statistical importance of the naturalized species to each other, and to the indigenous flora; the influence of climatal and geognostic conditions in facilitating or retarding distribution, and in developing aberrations from the original type, are attractive subjects of vast importance to the phyto-geographical student, and at the present time could probably be worked out more clearly and with greater precision for this colony than for any other country whose flora is equally well determined, owing to the small admixture of error with the facts upon which the student must base his conclusions.
The following plan has been adopted for expressing the known facts for each species, in a concise manner, and admits of ready adaptation for other districts.
I.—Extent of Diffusion.
With the view of indicating, as precisely as practicable, the present diffusion of each species, that Province of Auckland, as far south as Ngarua-wahia, has been divided (somewhat arbitrarily) into districts, as under:—
North Cape:—from Cape Maria Van Dieman and the North Cape, to Hokianga and the Bay of Islands.
Whangarei:—from Hokianga and the Bay of Islands, to Cape Rodney and the north head of the Kaipara harbour.
Waitemata:—from the south head of the Kaipara, and Cape Rodney, to the head of the Manukau harbour at Penrose, and the Tamaki at Panmure.
The Islands:—including the Cavalhos and Taranga groups, the Great and Little Barriers, etc., the Kawau, and those in the Firth of Thames.
Cape Colville:—the Cape Colville peninsula as far south as Kawæ-ranga and Wangamata Bay.
Waikato:—from Penrose and Panmure to Whaingaroa and Nga-ruawahia.
The district in which each species is known to occur will be indicated by the use of the numbers prefixed above; thus practically affording a separate list of the naturalized plants of each district; but it must not be supposed that these lists are complete, even for any one district. The naturalized plants of the western side of the North Cape district are quite unknown to the writer, and to a great extent those of the western side of the Whangarei district. The districts for which the lists are most complete, are Auckland, the Islands, and Cape Colville. Very little is known of the naturalized plants of the western and extreme southern divisions of the Waikato district, or of the East Coast, south of Wangamata Bay.
II.—Introduction Of Plants.
This has evidently been effected by two chief causes; the direct agency of man, for the purposes of cultivation; and the indirect agency of man and the lower animals, etc.
The first head may be sub-divided into:—
Horticultural (Hor.), * remains of, or escapes from garden cultivation, as Pelargonium quercifolium, Iris germanica.
Agricultural (Agri.), remains of, or escapes from, field cultivation, as Lolium perenne, Trifolium repens.
Accidental. (Acc.) Under this head are included those plants unintentionally introduced by man, whether mixed amongst seeds of ordinary cultivated plants, as in the case of buck-wheat, corn cockle, etc.; or from the seeds being able to attach themselves to clothing, or to the skins of animals, as the various docks, mallows, etc.; or from less prominent causes: in this way Erigeron canadensis has been carried all over the world.
Uncertain. (Unc.) Plants introduced by causes not directly referable to either of the above.
III.—Degree of Establishment.
As has already been stated, there is a wide difference in the degree to which naturalized plants have adapted themselves to the new conditions under which they are placed. It is attempted to estimate the extent of this adaptiveness by the application of the following terms:—
Denizen. (Den.) Plants thoroughly established, and spreading widely without assistance from man; often displacing indigenous forms to a great extent, or readily amalgamating with native species, as Trifolium minus, Erigeron canadensis, Poa annua.
[Footnote] * The abbreviations in parentheses are employed in the list.—ED.
Colonist. (Col.) Plants which maintain their ground where introduced, increase with more or less rapidity, but do not displace native species to any great extent, as Œnothera stricta, Tragopogon porrifolius.
Alien. (Ali.) Plants which maintain their ground where introduced, but are obviously incapable of wide diffusion, except by the direct agency of man, as the fig, potato, tomato, etc.
In order to afford a concise description of the usual habitat of each species, the following series of terms has been adopted, as they are for the most part identical with those employed for the same purpose in another paper, a brief explanation only is requisite. *
Littoral. (Lit.) Plants of the sea-shore, whether growing on sand or mud.
Ericetal. (Eri.) Plants of dry open land.
Pascual. (Pas.) Plants of grassy land, paddocks, etc.
Agrestal. (Agre.) Plants of cultivated land.
Rupestral. (Rup.) Plants growing on or amongst rocks.
Viatical. (Via.) Plants growing on waste places, or by road sides, etc.
Inundatal. (Inu.) Plants growing by the sides of streams and other places liable to inundation.
Paludal. (Pal.) Plants usually growing in wet soil, or in water.
Lacustral. (Lac.) Aquatic plants, submerged or floating.
Septal. (Sep.) Plants of thickets and hedge-rows.
Sylvestral. (Syl.) Forest plants.
A. Annual. B. Biennial. P. Perennial.
It will occasionally occur that a variety of information which cannot properly be placed under either of the preceding divisions is available, in which case it will be appended as a paragraph.
[Footnote] * See ante, p. 96, On the Botany of the Thames Goldfield.