OUR HOMES. 73 



Plants obtain these, their constituent elements, by absorption 

 through the pores of their roots and leaves. Hence, everything 

 which can contribute to their nourishment — all their nutriment — 

 must be either liquid or gaseous. Plants receive their oxygen and 

 hydrogen from water. They absorb carbon in the. form of carbonic 

 acid, which is an unfailing constituent in our atmospheric air and 

 spring water, and is formed in every soil that contains organic 

 matter. This carbonic acid is a kind of air which is constantly 

 produced in vast quantity by the three great chemical processes 

 most universally diffused in nature — the respira^tion of men and \ 



animals, the combustion of wood, coal, &c., and the putrefaction 

 or decay of animal and vegetable matter. It is evolved by fer- 

 mentation of liquids ; and it streams forth from the earth in vol- 

 canic action. All the carbonic acid generated by these different 

 processes is taken up into the air. If it should continue there 

 the air must of necessity become unfit for respiration. But in the 

 present balance of nature's forces, it does not remain there in exces- 

 sive quantity. The vegetable world discharges the functions of 

 supporter and protector of animal life — as supporter, by providing 

 the animal kingdom with nourishment — as protector, by absorbing 

 carbonic acid, retaining the carbon to build up its structure, and 

 exhaling pure oxygen during the light of day. 



There was a time in the existence of the earth, when the atmos- 

 phere was so charged with carbon that no animal life of a high 

 order could exist. Then all portions of the earth's surface had a 

 torrid climate, which favored an excessive growth of vegetation. 

 Subsequent geological changes buried the remains of that vege- 

 tation, and locked up a vast amount of carbon in the coal- • 

 measures as they now exist. Vegetation, as we now see it upon 

 the earth, holds another considerable portion of the original 

 quantity, so that for a time the atmosphere has been so far puri- 

 fied of this gas, as to sustain a high order of animal life. 



The atmosphere contains nearly all the essentials to plant 

 growth ; for it holds nitrogen in the form of ammonia, which is a 

 volatile gas continually rising from the decay of animal and vege- 

 table substances, and which seems to be the force power in the 

 growth of plants ; and all these elements may be absorbed by the 

 leaves directly from the air ; and .some recent observations go very 

 farto favor the hypothesis, that plants do take in a considerable 

 portion of their food in this way. These several elements exist- 



