Island Life; Or, The Phenomena and Causes of Insular Faunas and Floras

by Alfred Russel Wallace

[186] The large collection of fossil plants from the Tertiary beds of New Zealand which have been recently described by Baron von Ettingshausen (Trans. N. Z. Inst., vol. xxiii., pp. 237-310), prove that a change in the vegetation has occurred similar to that which has taken place in Eastern Australia, and that the plants of the two countries once resembled each other more than they do now. We have, first, a series of groups now living in Australia, but which have become extinct in New Zealand, as Cassia, Dalbergia, Eucalyptus, Diospyros, Dryandra, Casuarina, and Ficus; and also such northern genera as Acer, Planera, Ulmus, Quercus, Alnus, Myrica, and Sequoia. All these latter, except Ulmus and Planera, have been found also in the Eastern-Australian Tertiaries, and we may therefore consider that at this period the northern temperate element in both floras was identical. If this flora entered both countries from the south, and was really Antarctic, its extinction in New Zealand may have been due to the submergence of the country to the south, and its elevation and extension towards the tropics, admitting of the incursion of the large number of Polynesian and tropical Australian types now found there; while the Australian portion of the same flora may have succumbed at a somewhat later period, when the elevation of the Cretaceous and Tertiary sea united it with Western Australia, and allowed the rich typical Australian flora to overrun the country. Of course we are assuming that the identification of these genera is for the most part correct, though almost entirely founded on leaves only. Fuller knowledge, both of the extinct flora itself and of the geological age of the several deposits, is requisite before any trustworthy explanation of the phenomena can be arrived at.

[187] The following are the tropical genera common to New Zealand and Australia:—

1. Melicope. Queensland, Pacific Islands.

2. Eugenia. Eastern and Tropical Australia, Asia, and America.

3. Passiflora. N.S.W. and Queensland, Tropics of Old World and America.

4. Myrsine. Tropical and Temperate Australia, Tropical and Sub-tropical regions.

5. Sapota. Australia, Norfolk Islands, Tropics.

6. Cyathodes. Australia and Pacific Islands.

7. Parsonsia. Tropical Australia and Asia.

8. Geniostoma. Queensland, Polynesia, Asia.