STRUCTURE. 51 
and it is from these, absorbed by the plant, that 
it manufactures by the further aid of the hydro- 
gen and oxygen of which the water is itself 
composed, and of carbon obtained chiefly from the 
air, that which constitutes its own substance. 
We may call these various substances the raw 
materials used by the plant in its process of 
manufacture, and it obtains them all either in a 
liquid or a gaseous state, transmuting them into 
solids for the purposes of its own solid structure. 
We have seen that the substances in the earth 
upon which the plant feeds are all—in a liquid 
form—absorbed by the root hairs exercising 
the power of capillary attraction, and conveyed 
into the plant by the exercise of the same power 
of attraction, which continues until the liquid 
matters have reached their proper destination. 
But to enable the plant to assimilate the vari- 
ous matters which it derives from the soil and 
from the air, there must necessarily be a pre- 
existing structure; and by microscopical exami- 
nation and the aid of the science of chemistry, we 
are enabled to ascertain the form of this structure 
and the nature and quality of the substance of 
