PLANT SOCIETIES 319 
transpiration during the summer (or in regions like South- 
ern California in the rainy season) and a greatly reduced 
surface during the winter (or the dry season). 
In the case of trees the reduction of surface is brought 
about by the fall of the leaves (Sect. 186), and in the case 
of herbaceous perennials it is secured by the death of the 
green stem and the leaves, so that only a compact root, 
rootstock, or bulb is left alive underground. That is to 
say, the perishable or annual part of tropophytes has the 
characteristics of mesophytes or-even of moisture-loving 
plants, while the perennial part is constructed on the plan 
of xerophytes. 
391. Halophytes.— A halophyte is a plant which can 
thrive in a soil containing much common salt or other 
saline substances. The seaside obviously occurs to one as 
the region of halo- 
phytic vegetation, 
but many inland 
areas contain halo- 
phytic plants, for 
instance the neigh- 
borhoods about salt 
springs and the 
“alkali” lands of 
the southwest and 
the Pacific Slope. 
The presence of salt 
in the soil renders Fic. 226. — The Mangrove, a Halophytic Tree of 
: Southern Florida and the Tropics. 
absorption of the 
soil-water comparatively difficult, since osmosis takes place 
more readily between ordinary water and the liquid 
