ther, 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
finally kill it. The remedy for this is to spray the leaves frequently
so as to keep the air about them moist and so check transpiration.
Keeping a vessel of water near them helps also as this tends to keep
the air moist. Dust sometimes chokes the leaves. Washing or spraying
remedies this.

Sometimes house plants, and out-door plants as well, become covered
with a small, green insect called the plant louse or aphis. This
insect has a sharp beak like a mosquito and it sucks the juices from
the leaf and causes it to curl up, interfering with its work and
finally killing it. Frequent spraying with water will tend to keep
these away. A surer remedy against them is to spray the plants with
weak tobacco water made by soaking tobacco or snuff in water, or to
fumigate them with tobacco smoke. Sometimes the under side of the
leaf becomes infested with a very small mite called red spider
because it spins a web. These mites injure the leaf by sucking sap
from it. They can be kept in check by frequent spraying for they do
not like water. If, then, we are careful to frequently spray the
leaves of our house plants we will have very little trouble from
aphis, red spider or over transpirat