Greenhouses vary as much in style and cost as dwellings. The simplest is
any tight enclosure, covered with a glass roof at an angle of forty-five
degrees, facing the south, and kept warm by artificial heat. The
temperature is not allowed to be lower than forty nor higher than
seventy degrees of Fahrenheit; this will keep plants growing and make
them blossom, and affords a good place for starting plants to be
transplanted to out-door hotbeds, and finally to the vegetable garden,
after frosts are over. There is but one main danger in greenhouse
culture, and that is obviated by a little care: it is, allowing the air
to become too much heated for the health of the plants; they require but
little heat, but need it regularly. Some greenhouses are warmed by
stoves, and serve a good purpose; others have a stove set in a flue
which is built in the wall, gradually rising until it has passed around
two or three sides of the building. Place three or four sheet-iron pans
over this flue, at different points, and keep them filled with water;
the fire in the flue will heat the water, and impart both warmth and
humidity to the atmosphere, which is very favorable to the health and
growth of plants. Such a house is favorable to the growth of tender
exotic fruits and plants. A similar house without any artificial heat
affords an excellent place for the cultivation of the finest varieties
of foreign grapes.