280 Transactions. — Botany. 



to offer a suggestion as to the causes which had led to the 

 evolution of this xerophilous vegetation. In the first place, 

 he considered its extreme xerophytic character to be not at 

 all in accordance with its present environment, especially as 

 far as climate was concerned. He therefore turned to the 

 geological history of New Zealand, and based his conclusions 

 on the theory of Captain F. W. Hutton* — viz., that a great 

 elevation of the land took place during the Pliocene period, by 

 which the Southern Alps would be raised to a height much 

 greater than the present; and, to quote from Captain F. W. 

 Hutton's latest utterance,! "All the islands were joined 

 together, and the land stretched away to the east and south 

 so as to include the Chatham and Auckland Islands, as well, 

 perhaps, as Campbell and Macquarie Islands, whilst to the 

 north it certainly extended to the Kermadecs, and perhaps 

 much further. On the mountains of the South Island large 

 glaciers were formed, and the torrential rivers running from 

 them tore into disconnected fragments the Miocene marine 

 rocks which obstructed their valleys." According to Diels 

 this elevation of the mountains would lead to a much smaller 

 rainfall on the then high table-lands and plains stretching to 

 the mountains of the Chatham Islands in the east, and the 

 consequence would be a steppe climate. J 



As a consequence of the extreme dryness of this region 

 many of its plant inhabitants would migrate to wetter 

 localities, while those that remained would become either 

 modified so as to resist the gradually increasing drought or 

 would perish. Those plants which became so adapted Diels 

 calls " the descendants of the forest flora, "§ and he points out 

 in support of his argument how Schenk and Warming have 

 shown that lianes of the forest can become shrubs of the 

 plain. || Captain F. W. Hutton also considers the above 

 suggestion worthy of examination, for he writes (I.e., p. 182) : 

 "It is possible that this large extension of land to the east- 

 ward may have produced desert- or steppe-like conditions in a 

 portion of New Zealand, evidence of which some botanists 

 think they find in our flora." 



If we accept these views of Diels and Hutton, then three 



* First propounded in Trans. N.Z. Inst., vol. v., p. 385; further 

 elaborated Trans. N.Z. Inst., vol. viii., 1876, p. 383, et seq., and ia Annals 

 and Mag. of Nat. Hist., ser. v., vol. xv., p. 77, et seq. 



t"The Geological History of New Zealand" (Trans. N.Z. Inst., 

 vol. xxxii., 1899, p. 182). 



I I.e., p. 296. 



§ I.e., p. 246, " Abkommlinge der Waldflora." These inolude certain 

 species of Clematis, Pittosporum, Rubus, Carmichaelia, Notospartmm, 

 Aristotelia, Hymenanthera, and Corokia. 



[j See also remarks in this paper re Rubus pauperatus and Pitto- 

 sporum rigldum. 



