182 
NORTHERN GLACIAL ZONE 
Grampians. The more strictly alpine plants do not descend 
into the plains, though they often occur as sea-coast plants, 
or (in the tropics) as epiphytes (see p. 175). 
The conditions of life in this region resemble those of 
the arctic regions sufficiently nearly to enable the same 
species to live in both. The air is moister in the alpine 
region, especially in the lower part, but the low barometric 
pressure favours transpiration ; the light is more intense 
than at low levels, and on high plateaux is more or less 
circumpolar ; the vegetative season is short ; the soil is liable 
to extremes of cold or heat ; there is much wind ; the fre- 
quent presence of clouds diffuses the light and saturates the 
air at certain times. 
The composition of the flora depends upon the soil and 
other conditions, though the plants themselves are all more 
or less xerophytic. Upon the high-level plateaux where the 
soil is cold and wet the dampest parts are occupied chiefly 
by peat-forming mosses, but on the firmer parts of the 
peaty soil occur species of Tuncus, Eriophorum, Eleocharis, 
Carex, Scirpus, Festuca, Nardus, &c. All these show a 
more or less centric structure. Circumpolar light is very 
marked in such localities, and some authors regard the form 
of these plants as a direct result of its action ; whether this 
be so or not they are well suited to make the best use of it. 
Most of them contain large air-spaces, intercellular or 
enclosed by the leaves ; these are sometimes regarded as 
protections against cold (cf. p. 161), the air they enclose being 
warmer than the outside air. On the summits of the ridges, 
where the soil is drier and more rocky, the vegetation con- 
sists largely of such plants as Calluna, Loiseleuria, 
Vaccinium, Arctostaphylos, Gnaphalium, Empetrum, Lyco- 
podium, &c. All are pronounced xerophytes, usually 
evergreen, and thus the winter’s cold becomes perhaps the 
most important factor in their life. Most of them have 
more or less inrolled leaves, which perhaps, as we have seen, 
act as a protection against the cold ; at the same time these 
leaves have palisade tissue almost all round and stand more 
or less erect, so that they are well suited to the circumpolar 
light. Such leaves are termed by Jungner cold-leaves. 
There is no perpetual snow in the Grampians, but heaps 
of snow lie until July or August in hollows on the mountains, 
