_Pits and Frames._--These are used both for the summer growth and winter protection of various kinds of ornamental plants, for the growth of such fruits as cucumbers, melons and strawberries, and for the forcing of vegetables. When heat is required, it is sometimes supplied by means of fermenting dung, or dung and leaves, or tanner's bark, but it is much more economically provided by hot-water pipes. Pits of many different forms have been designed, but it may be sufficient here to describe one or two which can be recommended for general purposes.
[Illustration: FIG. 10.--Ventilated Plant Pit.]
An excellent pit for wintering bedding-out plants or young greenhouse stock is shown at fig. 10. It is built upon the pigeon-hole principle as high as the ground level a, a, and above that in 9-in. brickwork. At a distance of 9 in. retaining walls b, b are built up to the ground level, and the spaces between the two are covered by thick boarding, which is to be shut down as shown at c in cold weather to exclude frost, and opened as shown at d in mild weather to promote a free circulation of air through the pit. The height of the pit might be reduced according to the size of the plants; and, to secure the interior against frost, flow and return hot-water pipe e should pass along beneath the staging, which should be a strong wooden trellis supported by projections in the brickwork. The water which drains from the plants or is spilt in watering would fall on the bottom, which should be made porous to carry it away. For many plants this under current of ventilation would be exceedingly beneficial, especially when cold winds prevented the sashes from being opened. A pit of this character may be sunk into the ground deeper than is indicated in the figure if the subsoil is dry and gravelly, bat in the case of a damp subsoil it should rather be more elevated, as the soil could easily be sloped up to meet the retaining wall.
_Frames._--Frames (fig. 11) should be made of the best red deal, 1¼ in. thick. A convenient size is 6 ft. wide, 24 in. high at the back and 15 in front; and they are usually 12 ft. long, which makes three lights and sashes, though they can be made with two lights or one light for particular purposes. Indeed, a one-light frame is often found very convenient for many purposes. The lights should be 2 in. thick, and glazed with 21 oz. sheet glass, in broad panes four or five to the breadth of a light, and of a length which will work in conveniently and economically, very long panes being undesirable from the havoc caused by accidents, and very short ones being objectionable as multiplying the chances of drip, and the exclusion of light by the numerous lappings; panes about 12 in. long are of convenient size for garden lights of this character. In all gardens the frames and lights should be of one size so as to be interchangeable, and a good supply of extra lights (sashes) may always be turned to good account for various purposes.