The Elements of Agriculture

tion of the sap--and that of evaporating its water. If we examine leaves with a microscope we shall find that some have as many as 170,000 openings, or mouths, in a square inch; others have a much less number. Usually, the pores on the under side of the leaf absorb the carbonic acid. This absorptive power is illustrated when we apply the lower side of a cabbage leaf to a wound, as it draws strongly--the other side of the leaf has no such action. Young sprouts may have the power of absorbing and decomposing carbonic acid.

[What parts of roots absorb food?

How much of their carbon may plants receive through their roots?

What change does carbonic acid undergo after entering the plant?

In what parts of the plant, and under what influence, is carbonic acid decomposed?]

The roots of plants terminate at their ends in minute spongioles, or mouths for the absorption of fluids containing nutriment. In these fluids there exist greater or less quantities of carbonic acid, and a consider