THE PLANT AND ITS ENVIRONMENT 11 
The soil particles are composed of a number of different com- 
pounds. Small quantities of these go into solution in the water 
around the particles and pass into the roots of plants. The ele- 
ments which are necessary for plants and which are obtained 
from the soil are nitrogen, phosphorus, sulphur, calcium, iron, 
potassium, and magnesium. 
Habit and habitat. There are many different environments in 
which plants grow, and in each case the plants are fitted by their 
structure for their particular 
environment. The kind of 
environment in which a plant 
erows naturally is known as 
its habitat, while the form of 
the plant is spoken of as its 
habit. 
Terrestrial, aquatic, and 
epiphytic plants. Plants that 
grow in the ground, as is the Fia. 5. A floating aquatic plant (Pis- 
case with most of the higher gig stratiotes) that is found in the trop- 
plants, are terrestrial plants. ical and subtropical regions of both 
Those that have their habitat hemispheres. (x 4) 
in water are known as aquatic 
plants, or aquatics (Figs. 5, 72, 217). If they are submerged in 
the water, they are submerged aquatics. Those that grow perched 
on other plants but obtain no nourishment from the plants on 
which they grow are epiphytic plants, or epiphytes (Figs. 2, 85, 
195, 490, 493, 506, 507). In cold temperate regions the epiphytes 
are mosses and mosslike plants and lichens. In warmer regions, 
particularly in the moist tropics, many flowering plants also grow 
as epiphytes. Some of the most beautiful of the orchids belong 
to this class (Fig. 2). Epiphytes are dependent for their water 
supply on rain and on water which condenses from the atmosphere. 
Xerophytes, mesophytes, and hydrophytes. Plants that are 
fitted for growing in a dry habitat are known as zerophytes 
(Figs. 511-514). The cacti are good examples (Fig. 512). These 
plants have enlarged stems in which they store water for use 













































