‚rocks of the slopes disintegrated, they would be readily colonized in the wet 
178 General Remarks on the High Mountain Vegetation. 
would, as DIELS was the first to point out, assume more xerophytic structure 
and the xeromorphic growth-forms (the divaricating, flat-stemmed leafless, cu- 
pressoid &c.) have arisen, while on the eastern mountain-slopes the drought- 
conditions would be still more severe and sufficient to have evolved the great 
Raoulia cushions. With the retreat of the glaciers on the W., as the bare 
climate by the neighbouring plants, just as is happening now, while forest 
would by degrees advance from the coastal-plain to the ER DER On the 
E. the struggle between disintegration and plant-occupation would be far more 
‚severe, the plant-covering nevertheless increasing slowly in area. This struggle 
still goes on, river-fans in particular exhibiting every stage of occupation, 
destruction and rejuvenescence of their plant-covering. But now man as an 
agent of destruction has appeared and he is rapidly undoing the work of 
thousands of years, and has already converted much of Central Otago into 
. veritable desert! 
5. The erakal Conditions of the High Mountains. 
High mountains the world over are subject to a set of similar and fairly 
definite conditions which there is no need to discuss here. On.the other hand, 
those specially rs New Zealand need brief Here so far as N are. 
‚known or suggested. 5 
No accurate details are ae ah the high-mountain u It 
s clear however that the species are not attuned to nearly so great intensity 
of cold as are alpine plants in general. This is clearly brought home by the 
fact that many species of the alpine belt cannot endure the winter temperature 
of Kew and hardly any that of Berlin. Probably — 18°C. is more than most 
can endure. Certainly, a protecting snow-covering stands for. a good deal, but 
many species tolerate equally well snowy and snowless stations (e.g. — Veronica 
 Pinguifolia (agg.), V. epacridea, ee N) vn many of the Koi bee 2 
Bao are never completely buri: 2 “ARE 
The amount of rain and ehe as number of rainy- die is ink grea er 
RR in the lowlands, while, in addition mist and cloud?) are frequent. The 
abundance of vegetation at above 800 m in Central Otago, below which alti- 
tude the induced dı PERS U Be a learly « ea re 
E 
But it. must a be - coneluded that in an nn wet clima li 
one has to. be most arehul ‚eng BER 
‚extremely un during 
