INFLUENCE OF ENVIRONMENT 275 
gradual. As in Eucalyptus it is not uncommon fo find 
a reversion to the original leaf-form on young shoots of 
the older trees. 
Similar in their behavior to desert plants are the 
“Halophytes,” those growing along the seashore or in 
salt marshes. Thus the sea-rocket (Cakile), samphire 
(Salicornia), ice-plant (Mesembryanthemum), and other 
maritime plants show these peculiarities. These plants 
have fleshy stems and leaves and can live with very 
little water. The explanation of this peculiarity in 
plants growing where there seems to be an abun- 
dance of water, has been thought to be the fact that 
the separation of the water from the salt solution is 
difficult, and, moreover, the accumulation of salt within 
the tissues of the plants, if free transpiration of water 
from the surface took place, would be injurious to the 
plant. 
EPIPHYTES 
Under the name Epiphytes are included those plants 
which grow attached to others, but are not parasites. 
While these epiphytes usually grow upon trees or other 
plants, not infrequently they may attach themselves to 
rocks or other inanimate objects. Epiphytic plants are 
most abundant in the moist, hot regions of the tropics, 
but are by no means confined to these, since many 
mosses, lichens, and liverworts which occur plentifully 
in the temperate or even arctic regions, may be prop- 
erly classed as epiphytes. Of the ferns and flower- 
ing plants, however, very few epiphytic types occur 
outside the tropics, though there they form a most 
characteristic feature of the vegetation. 
