12 FLOWERING PLANTS 
The buds of Xerophytes are protected against extreme heat 
by. being deeply sunk among the leaves, or they may be 
situated in a groove in the stem. The stamens are usually 
conspicuous, as there is no fear of the pollen being washed 
away by the rain. The seeds, which need to be protected 
from severe droughts, are enclosed in hard, woody fruits, which 
in many cases open out only in the damp to let out the seeds. 
In the tropics many Epiphytes—i.c., plants which grow 
upon others without obtaining their nourishment from them— 
are xerophytic, as, for instance, many orchids with aerial 
roots. The Epiphytes in Britain are not as a rule Flowering 
Plants, but belong to lower groups, such as Mosses, Lichens, ete. 
Character.  Mesophytes are a very large group of plants. 
istics of T'hey include the thousands of common herbs 
Mesophytes. found in meadow and pasture, on moor and _ hill, 
the shrubs of our hedgerows, the trees of wood and forest. 
They offer every variety of habit: some are creeping, others 
climbing ; some love shade, others require much light, but all 
agree in demanding a fair supply of water. Mesophytes are 
not sharply marked off from Xerophytes on the one hand, or 
from Hydrophytes on the other; there is no possibility of 
confusing a Xerophyte and a Hydrophyte, but there is a 
gradual transition between the Mesophytes and these other 
groups: they merge into each other, 
Speaking broadly, Mesophytes differ from Xerophytes in 
their regular and constant transpiration, hence the structure 
of the leaf is different. In the Mesophyte the lamina is 
_ usually thin, expanded at right angles to the direction of light ; 
stomata -abound on the lower surface, and sometimes occur 
also on the upper—in short, there is every facility for trans- 
_piration. The chief advantage of thorotgh transpiration is 
that it accelerates the distribution of water and dissolved 
food substances through the plant. Food substances, it must be 
remembered, can enter only in dilute solutions, so that a great 
deal of water has to be absorbed in order that the plant may 
get sufficient food, consequently the plant must be able to get 
rid of water. 
