INFLUENCE OF WATER ON PLANT-LIFE 31 
3. Mesophytes. 
Some plants are pronounced hygrophytes, others pro- 
nounced xerophytes. Hygrophytes lie, in their relation 
to water, at one end of a series which is terminated at 
the other extremity by the highly specialized xerophytes. 
Between the two lie a vast host of plants, generally 
known as mesophytes, which possess no marked char- 
acters either way. Such plants live in conditions which 
are fairly favourable to the plant all the year round. 
The true mesophyte is an evergreen, and lives only in 
the Tropics or in regions not far removed from them. 
Any winter-break would entail the assumption of some 
more or less marked xerophytic characters. We have 
no true mesophytes in Great Britain because the inter- 
ruption of winter is too pronounced. The nearest plants 
we have to them are certain marsh-plants like the 
iris. If the winter is mild, the leaves of the iris persist 
to the spring. The leaves are long, band-shaped, and 
erect. The latter is a xerophytic character (p. 46). Amid 
a host of hygrophytic characters, the iris, therefore, has 
at least one xerophytic character—it avoids the light 
by turning its leaves edgewise to it. If, however, the 
winter is severe, the leaves all perish, and the plant 
dies down to an underground stem, and behaves as a 
pronounced xerophyte. 
Tropophytes (Gr. tropos, change).—The great majority 
of our plants are tropophytes. Unlike evergreens, they 
exhibit one set of characters in summer and another 
during winter. They provide against drought by 
changing their mode of life at the approach of winter 
(see Chapter VI.). 
