To digest the starch and food sent up by the roots.
To do these things well leaves must be connected with a strong, healthy root system and must have plenty of light and air.
We are now ready to give reasons for the facts about leaves mentioned in the first part of the chapter (see [page 109]).
Leaves are green because the green coloring matter is necessary for the leaf to do its work.
Leaves are flat and thin and broad in order that they may present a large surface to the air and sunlight.
FIG. 61.
To show that growing leaves contain starch. 1. Represents a green cotton leaf as picked from the plant. 2. Is the same leaf after taking out the green coloring matter; the leaf is white. 3. The same leaf after treatment with weak iodine turned to a dark purple, showing the presence of starch. (Drawings by M.E. Feltham.)[ToList]
