corn, 13.
cowpea, 12.
depth of growth of, 12.
extent of growth of, 12.
habit of growth of, 11, 15.
hold plant in place, 9, 11, 15, 16.
important lessons from, 13, 15.
location of, 12, 13.
need firm soil, 20, 22, 23.
need mellow soil, 20, 22, 23.
need moist soil, 20, 22, 23.
need plant food in soil, 20, 22, 23.
need warm soil, 20, 22, 23.
need air in soil, 21, 22, 23.
produce new plants, 10, 11.
rapidity of growth of, 15.
soy-bean, 12.
store food, 10, 11.
sweet potato, 13.
tree, 13.
uses of, 9, 10, 11, 15.
work of, 9, 10, 15.

Rotation of crops, 219.
benefits from, 230.
conditions which modify, 232.
effect upon fertility, 224.
examples of, 234.
general rules for, 233.
length of, 233.