New Zealand Plants and their Story
Origin of the Flora
Origin of the Flora.
Fig. 2.—The Great Brown Seaweed (D'Urvillea utilis), exposed at low water. Dog Island, near Bluff.
Lands Department.] [Photo, L. Cockayne.
Let us in imagination peer into that remote past when New Zealand had finally emerged from the ocean, and when its surface, destitute of all life, was ready to receive its plant and animal immigrants.
Now, it is quite impossible to estimate geological time from figures. When we try to think of millions of years, our minds become confused; and so those long periods during which the earth gradually assumed its present form are designated by certain names representing divisions of geological time. These have been classified according to the fossils contained in the rocks. The divisions are five in number, and are named respectively, beginning with the earliest—the Archaean, the Primary, the Secondary, the Tertiary, and the Quaternary or Recent. These, again, are divided into smaller subdivisions, each, however, still of an unthinkable age.
With the first two great divisions we have nothing to do here. The history of our plants commences at that subdivision of the secondary period known as the Jurassic, when there flourished on the earth in general cycads, ferns, horse-tails, and pine-trees. The ancestors of the present crayfish and molluscs then lived in the seas, and huge reptiles wandered through the moist forests. Those plants which are propagated by means of the minute bodies known as spores—ferns and mosses, for instance—are able to travel vast distances by means of the wind, and, if the conditions are favourable, they soon gain a footing on unoccupied ground. Thus it is quite easy to account for the presence of the same species of the lower groups of plants in many lands far distant from one another. But when one comes to deal with the more highly organized seed-plants, whose seeds could travel over a vast body of water only by the merest chance, and with animals in general, many of which are still less adapted for ocean transit, speculations as to great changes having taken place on the surface of the globe come into play, and former land-connections between regions now separated by the broad ocean have to be assumed.page 5
Without going into details, zoological and botanical statistics and evidence show clearly enough that New Zealand has received its plants from two main sources—(1) the Malay Archipelago and Australia taken together, and (2) South America, together with a problematical land-area" existing in Tertiary times in the Southern Ocean, of which ice-bound Antarctica, and even portions of New Zealand itself may have been parts.
According to geologists, the land-surface of New Zealand underwent great changes during Tertiary times; at one period reduced to quite a small group of islands, and at another, the land having risen hundreds of feet, stretching north, east, and south, and uniting the scattered members of the archipelago to the main islands. How far "Greater New Zealand," as it may be called, extended is a matter of conjecture, but naturalists are generally agreed that it was joined to Australia and the Malay Archipelago by way of New Caledonia and the New Hebrides. The chief.matter in dispute is whether there has ever been an actual land-connection with South America.
Now, although the author has, in certain of his writings, favoured the idea of a New Zealand-South American union, there is a good deal to be said against the view, especially from the geological standpoint. Perhaps the strongest evidence that a "bridge" to South America existed lies, as Dr. W. B. Benham, F.R.S., has shown, in the presence in New Zealand of a family of South American earthworms—animals which certainly could not travel over the ocean. A spider hitherto found only on those distant granite rocks, the Bounty Islands, is allied not to any existing Australian or New Zealand species, but to a South American family. Galaxias, a genus of fresh-water fishes, occurs chiefly in South America and New Zealand, while there is also a species in South Africa. There is much more zoological evidence, but this will give the reader a sufficient idea as to its character.
Evidence derived from a study of plant-distribution can never by itself be regarded as conclusive, since there are various means—such as birds, ocean-currents, floating logs, icebergs, and the wind—by which seeds can be conveyed over the ocean. But the greater the distance to be traversed, the less likely are they to be carried in this manner. Heavy seeds, such as those of the kowhai, could not be blown by the wind for thousands of miles, and yet our plant of that name is identical with one growing in Chile. Our fuchsias, calceolarias, beeches, and a number of other plants have their headquarters in page 6South. America, and must either have come thence to New Zealand, or have reached both, these regions from the old problematical con tinent of the south.
Besides the kowhai, a number of other species are common to New Zealand and Fuegia. The following are some of the more important: Veronica elliptica, a shrubby speedwell, confined to the coast of the South. Island, to one locality north, of Cook Strait, and to the New Zealand subantarctic islands;. Grassula moschata, a rather small succulent plant with, red stems, common on many parts of the South. Island coast, Stewart Island, the subantarctic islands, and Chatham Island; Colobanthus quitensis, a tiny plant of the pink family, occurring in some parts of the South Island mountains; Coriaria ruscifolia, the tutu; Gcurm parviftorum, a pretty white-flowered plant of the subalpine and alpine region;' Luzuriaga marginata (fig. 3), a beautiful little plant, growing amongst moss in forests, and bearing a large white berry, found at sea-level in Southland, Stewart Island, and Westland, but only in subalpine forests in the North Island; two small species of rush, J uncus scheuzerioides and J. novae-zelandiae; one of the wood-rushes, Luzula racemosa; South America two sedges, Carex Darwini var. urolepsis, which up to the present has only been recorded from Chatham Island, and one of large size, C. trifida.
Oxalis magellanica, a pretty white wood-sorrel, occurs in New Zealand, South America, and East Australia. A number of other plants are so closely related as to be virtually common to these three regions. Finally, Macquarie Island is an interesting case, since no fewer than thirteen of its twenty-eight species of ferns and flowering-plants belong to South America or to the chain, of distant subantarctic islands.page 7
Quite recently, through the explorations of the Swedes in the first place and of Sir Ernest Shackleton in the second, it has been proved beyond doubt that forests containing both subtropical and temperate trees existed during Tertiary times in Antarctica. On Seymour Island, which is virtually a part of the antarctic continent, latitude 64° south, the Swedish Antarctic Expedition discovered a number of impressions of leaves in the sandstone rock. These have since been identified, and in some cases the species show strong relationships to plants living at the present time in South America, New Zealand, and Australia. Most interesting to us is the unlooked-for presence of a fossil Knightia allied to the rewarewa (Knightia excelsa), a tree found only in New Zealand, though there are in New Caledonia two other species of the genus, but belonging to a different section. Then, too, there is the genus Drimys, with the living Drimys axillaris (the pepper-tree), and two other New Zealand species; while D. Winteri (the Winter's bark) and D. aromatica are respectively Fuegian and Tasmanian representatives. Laurelia, a genus of only two species—one in Chile, and, the other L. novae-zelandiae, the wellknown puketea of the New Zealand northern forests—occurred in the forests of Tertiary Antarctica. Araucaria braziliana, of subtropical Brazil, and A. Bichvillii, of Australia, are closely related to a fossil araucaria, while the well-known monkey-puzzle tree of Chile (A. imbricata), the Norfolk Island pine (A. excelsa), and certain New Caledonian trees belong to the same genus. Other examples could be cited, but sufficient has been said, to show that the remarkable discoveries of the courageous explorers strengthen the evidence in favour of land-connection between New Zealand, Australia, and South America, while the existence of an ancient antarctic vegetation, correlated, of course, with a much warmer climate, can no longer be denied.