162 Transactions of the South African Philosophical Society. 
occurs in the Arctic zone through the coldness and the freezing of 
the soil.* Itis consequently not surprising that comparatively few 
species only are common to the Arctic and Alpine regions, and that 
there is a great difference in the vegetation of both, not only as 
far as the species of plants are concerned, but specially also with 
regard to their general habit of growth and their external as well as 
internal structure. 
If we examine the vegetation of Alpine regions we find that it 
is characterised by the absence of trees, tall shrubs, and high 
herbaceous plants. On the other hand, new forms and modes of 
growth appear or become more numerous. Many plants produce 
no central stem but a large number of very short stems, packed so 
closely together that they form an almost solid cushion—a mode of 
growth well known among mosses—while others develop only a rosette 
of leaves close to the ground; almost all possessing a very large system 
of roots. There are other special features in their appearance. Their 
leaves are mostly hairy or leathery, which peculiarities are not pro- 
tections against the cold but against the heat; that is to say, they 
protect the plants against the loss of too much water during the 
hours or days when the surrounding air is hot and dry. 
We here at the Cape are, of course, familiar with many plants 
which secure their existence during the dry and almost rainless 
summer in a similar way; the silver-tree, the everlastings, and 
many other plants being protected by a coat of fur, while the 
Proteas illustrate the leathery foliage. These and many other 
peculiarities of structure in our vegetation are principally due to 
the necessity of regulating the transpiration of the leaves; they 
are characteristic of xerophilous plants. Consequently, while in 
Northern and Central Hurope.the xerophilous characters form the 
principal distinction between the vegetation of the lower and higher 
regions, we cannot expect this to be the case here, for protection 
against excessive transpiration is wanted in the valleys as well as on 
the mountain-tops. In fact, the climate of the higher mountains is 
moister than that of the plains. This is due partly to the snow which 
remains on some of the higher peaks for months, and appears on the 
Hex River range even as late as Christmas. Much more important 
in this respect are, however, the clouds which cover the mountains. 
during the south-east winds, for then considerable quantities of mois- 
ture are deposited, which gradually soaks into the ground and the 
fissures of the rocks, thus often feeding springs quite close to the 
top of a mountain. 
This greater amount of moisture causes the existence of a much 
* Schimper, Pflanzen-Geographie auf Physiologischer Grundlage, Jena, 1898, 
