Cockayne. — Development of Seedlings. 279 



those of P. betulimis, but in certain dry regions of the South 

 Island the intermediate shrubby, or I may call it the xero- 

 philous form, undergoes no further change, and is considered 

 by some botanists a distinct species.* On the contrary, the 

 Chatham Island plant, and perhaps also one of the North 

 Island varieties, passes through no xerophilous form. Here 

 again, then, the Chatham Island plant resembles the ancestral 

 form. There are few plants in New Zealand more xerophytic 

 in structure than the various species of Aclphijlla. The seed- 

 ling forms of A. squarrosa and A. colensoi have, however, 

 quite flaccid and grass-like leaves. In the Chatham Islands, 

 Mr. Cox tells me, Aciphylla traversii has leaves sufficiently 

 soft and flaccid for sheep to eat them greedily. Such an 

 Aciphylla would probably much resemble the ancestor of 

 the New Zealand forms. On the dry table -lands of the 

 South Island of New Zealand, and in various parts of the 

 North Island where the soil is poor and where the rainfall 

 is low, the character of the vegetation is xerophytic, many 

 of the shrubs showing, for instance, a common adaptation 

 to the environment in their much divaricating interlaced 

 wiry branches ; in fact, they resemble very much indeed 

 the semi -shrubby stage of Hoheria, Plagianthus betulinus, 

 Pennantia corymbosa, and Sophora tetraptera. Xerophilous 

 as these former shrubs are, a very slight change of environ- 

 ment, such as the shelter of a forest, will alter them in 

 the most marked manner (see above regarding Pittosporum 

 rigidum, and what follows re Rubus pauperatus). x\n extract 

 from my note-book, taken in the " bush" at the lower gorge 

 of the Waimakariri, is of interest in this connection : " Very 

 worthy of note is a young plant of Corokia cotoneaster" 

 — a most densely growing shrub under normal conditions — 

 " assuming a semi-tree-like habit. At this stage the stem is 

 erect, the branches pointing upwards and outwards, twisted 

 and drooping at their extremities. It much more resembles 

 the transitional form between the semi-shrubby stage of 

 P. betulimis and the mature form of that plant than it does 

 its own normal form as growing in the open." 



If the early seedling form of a number of these xerophilous 

 shrubs be examined it will be seen, as I have shown in some 

 instances,! that they are at first erect, with a much more con- 

 siderable leaf development than the adult, and altogether 

 better adapted for more hygrophytic conditions. That is to 

 say, the majority of the scrubby plants of river-terraces, stony 

 flats, and the like, might well be descended from ancestors 

 which lived in a moister climate. Dr. L. DielsJ was the first 



* Sophora prostrata, Buchanan. 

 f S°e, for instance, I.e., pp. 91, 92, 93. 



+ "Vegetations — Biologie von Neu-Seeland," Leipzig, 1S96, pp. 246, 

 247, and 296. 



