frame or hotbed, it will soon raise the
temperature in the hotbed to a point that will destroy the plants. It is
necessary, then, to pay close attention to the bed and, when the sun
shines, to slip the sashes down or raise them and place a block under
the upper end to allow the steam to pass off. The cold-frame also must
be aired when the sun shines, and the sashes must be gradually slipped
down in mild weather. Finally, they may be removed entirely on sunshiny
days, so as to accustom the plants to the open air, but they must be
replaced at night. For a while before setting the plants in the open
gardens, leave the sashes off night and day.

[Illustration: FIG. 86. GREENHOUSE AND COLD-FRAMES]

While the hotbed may be used for starting plants, it is much better and
more convenient to have a little greenhouse with fire heat for this
purpose. A little house with but four sashes on each side will be enough
to start a great many plants, and will also give room for some flowers
in pots. With such a house a student can learn to manage a more
extensive structure if he gives close attention to airing, watering, and
keeping out insects.

=Sowing.= The time for sowing the different kinds of seeds is an
important matter. Seeds vary greatly in their requirements. All need
three conditions--a proper degree of heat, moisture, and air. Some
seeds, like English peas, parsnips, beets, and radishes, will germinate
and grow when the soil is still cool in the early spring, and peas will
stand quite a frost after they are up. Therefore we plant English peas
as early as the ground can be worked.

But if we should plant seeds like corn, string (or snap) beans,
squashes, and other tender plants before the ground is warm enough, they
would decay.

Seeds cannot germinate in soil that is perfectly dry, for there must be
moisture to swell them and to start growth. The oxygen of the air is
also necessary, and if seeds are buried so deeply that the air cannot
reach them, they will not grow, even if they are warm and moist.

[Illustration: FIG. 87. GATHERING AND SHIPPING CELERY]

The depth of planting must vary with the character and size of the seed.
English peas may be covered six inches deep and will be all the better
for such covering, but if corn be covered so deep, it hardly gets above
the ground. In planting small seeds like those of the radish, cabbage,
turnip, lettuce, etc., a good rule is to cover them three times the
thickness of th