THE DISTRIBUTION OF PLANTS 103 
Adaptationto  luven in a comparatively limited district it is 
Surroundings. possible to collect instances of adaptation, some 
of which have already been noticed in other connections. The 
part of the plant which perhaps shows the greatest power ot 
adaptation is the leaf. In the Water-crowfoot, one kind of 
leaf is found in the part of the plant growing in water, 
another in that part of the shoot above water (p. 32). 
In Lady’s-mantle, the leaves of the species growing in 
meadows and pastures (Alchemilla vulgaris) are simple aid 
undivided, whilst the species growing on the tops of moun- 
tains (Alchemilla alpina) has leaves deeply divided into six or 
seven lobes, and each lobe bends inwards as though to catch 
the dew and drops of water more easily. 
Comparing tropical countries with temperate regions, we 
find a similar variety in the structure of the leaf. In the 
tropics, plants have to be able to resist a rainy season which 
may last four or five months ; it is important, therefore, that 
the surface of the leaf should be smooth, or even polished, so 
that water may run off easily, as in the India-rubber plant. 
In deserts, on the other hand, leaves must be able to collect 
all the water that falls, they therefore generally slope in such 
a way that the water must pass towards the stem and root 
(p. 29). 
In this connection we may ca the characteristics of 
plants that have to pass through a winter period (hibernation). 
They have stores of reserve material in the root, or stem, 
or leaves ; their buds are also well protected. If herbs, the 
buds are often underground; if trees, by bud-scales, resin, 
wool, etc. (pp. 16, 17). 
Those interested in the distribution of plants should read 
Willis on this subject (‘Flowering Plants — Ferns,” vol. i 
chap. iii.). 
8—2 
