STRUCTURE. 49 
and plant growth. Here we shall only attempt 
to state some of the principal facts which science 
has been able to establish—giving indeed so much 
as will naturally fall within the proportionate 
space which must be allotted to this part of the 
subject; yet enough, we trust, to satisfy all 
who have fairly comprehended the aim and 
object and the necessarily limited space of this 
volume. 
Plants, like ourselves, are composed of sub- 
stances which are drawn by absorption and in- 
spiration from the material world. Like ourselves 
they may be said to drink and to breathe—some 
even to eat. Like ourselves too, the matters 
absorbed and inhaled into their system are assi- 
milated by them for the purpose of supplying 
the waste and contributing to the growth of their 
bodies. Unlike ourselves, however, their ordinary 
processes of growth—after the termination of the 
early growth which we call germination—are un- 
attended by the production of heat which is not 
common to the earth or air or water in which 
their parts exist. They are indeed of the same 
temperature as the material substances which 
