SOME LESSONS IN BOTANY 55 
and in such a delicate organ as the leaf. Sunlight furnishes 
the energy for the process, and Nature has made the leaf 
thin and flat in order to expose as much surface to the sun- 
light as possible. In leaves that are kept in the dark by 
dense shade no starch is made, and, of course, the process is 
suspended in all cases at night. Another factor that is 
necessary is the presence of the green y 
coloring matter of leaves. Leaves that 
are white or colorless cannot make 
starch. 
The leaves are always a conspicuous 
part ofaplant. They help to give the 
plant its characteristic appearance and 
are one of the chief features by which 
we identify it. If we wish to have a 
speaking acquaintance with a good va- 
riety of plants, it is necessary to be 
observing about a great many details, 1."2."*" 
some of which we call attention tohere. +; « .” 
Surface and Color. — The surface of <:: FZ 
leaves may be glossy, smooth, hairy, ; 
rough, etc.; and their shade varies 
from a very dark green or bluish green :* food from ¥ HaSott.!”.: 
to light green, yellowish green, or even Diagram representing the 
golden yellow. , gnice of the leaves. 
Ribs and Veins. — These are the woody fibers that form 
the framework of the leaf and determine its shape. The 
leaf may be parallel-veined, as in Indian corn, the small 
grains, and the grasses, or it may be netted-veined, as in 
trees and shrubs and the majority of other plants. The 
details of the mode of veining are subject to infinite varia- 
tion, each species having its own characteristic plan that 
