36 BRITISH PLANTS 
Xerophytic Characters exhibited by Plants living under 
Physiologically Dry Conditions. 
The difficulty with xerophytes is to retain within the 
tissues sufficient water for their needs. If, from any 
cause, little is absorbed, then little must be lost. To 
secure this, the organs on which are found the exits for 
the escape of water are modified. 
Thus leaves and shoots are modified in form and 
structure, curious and characteristic habits of growth 
are assumed, and the display of the leaves to the light 
is not the same as in ordinary plants. 
Whatever the means adopted, the end is always the 
same—to keep down transpiration to a minimum, in order 
that as much water as possible may be retained within 
the body of the plant. 
1. Stunted Growth of Stems.—This is brought about 
by lack of nourishment, a condition experienced by all 
xerophytes whose water-supply is limited. Trees become 
stunted and dwarfed, assuming the low bush-form in 
regions where the xerophytic conditions become pro- 
nounced—e.g., in semi-deserts, on dry, windy plateaux, 
in cold alpine regions, and near the limits of tree-growth 
towards the Pole. Under extreme conditions, the trees 
may be only a few inches high, and the annual output 
of leaves not more than two or three. On the crests of 
Snowdon, the common juniper forms a great branching 
mat, lying prostrate on the rocks. The soil is thin, and 
the plants are exposed to violent desiccating winds, great 
heat at noon, severe cold at night, and intense illumina- 
tion when the sky is clear. The internodes are short 
and the development of buds is feeble and irregular. 
The mat-like growth serves to keep the plant just out of 
reach of the most violent wind, and at the same time 
keeps the soil underneath it shady and moist. 
This form of stunted growth is not, however, permanent, 
because under more genial conditions many stunted alpines 
will develop tall stems, while, on the other hand, plants 
which are several feet high on the plains shrink to a few 
inches on high alps and wind-swept downs (see p. 77). 
Although light has some effect in dwarfing plants by 
promoting transpiration, it has a direct effect upon 
growth, which is far more important. Shoots and leaves 
