water and oxygen given out on the rough side, and that side is turned
down toward the earth probably so that rain and dust will not choke
the little pores.

The leaves of the lower branches tend to spread out in a broad, flat
plane because in the effort to get light no leaf will grow directly
under and in the shadow of another, while on those branches which grow
straight up from the top of the tree the leaves can get light from all
sides and so arrange themselves around the stem.

Is it of any value to the plant grower to know these facts about
leaves? It is, for knowing these things he can better understand the
necessity of caring for the leaves of his growing plants to see that
their work is not interfered with.


HOW THE WORK OF SOME LEAVES IS INTERFERED WITH

Many people who grow house plants have trouble in keeping them well
clothed with leaves, for instance, the geranium and the rubber plant.
The leaves are constantly turning yellow and dropping off or drying
up. This sometimes occurs from over-watering or not sufficiently
watering the soil in the pot or box. If the watering is all right the
trouble may occur in this way: The air of the house is quite dry,
especially in winter. As a result transpiration from the leaf may be
excessive. More water is transpired than is necessary, consequently
more is pumped by the roots and with it more food is sent to the leaf
than it can take care of. As the excess of water is transpired the
excess of food is left in the leaf. The tendency is to clog its pores
and therefore interfere with its work, and gradually weaken and