492 



THE VILLA GARDENER. 



degree of heat is generally found enough, unless tropical 

 plants are to be grown. The roof may consist of three spans, 

 as shown in Jig. 372., each terminating in an angle, as shown 

 in fig. 373., on the apex of which are fixed the ornaments 

 represented in Jigs. 374. and 375. In Jig. 372., a is the 

 door, b the front without the glass to show the frame-work, 

 and c the other part of the front, with the glass in it to show 

 the form of the panes. 



SuBSECT. IV. — Hothouses. 



375 



376 



542. Hothouses differ from green-houses, chiefly in requiring more heat, 

 as they are intended for the growth of tropical plants; whei-eas green-houses 

 are intended for the plants of climates only a little warmer than our own. 

 Hence the temperature of a hothouse should be several degrees higher than 

 tliat of a green-house ; the lowest heat being from 55° to 60° even at night, 

 and rising in the middle of the day, partly by sun heat, to 80° or 90°, or higher 

 during summer. The great difference between the heat of the night and the 

 day, is one of the late improvements in horticulture. Formerly gardeners 

 kept their stoves at nearly the same heat night and day, though it was clearly 

 different from the natural habits of the plants, as the nights in tropical 

 climates are well known to be very much colder than the days. There are 

 many varieties of hothouses, but the most useful are the stove, the orchideous- 

 house, and the aquarium. 



543. The moist stove has generally a lean-to roof, as shown in^^. 376. ; and 

 those which were built some years ago had always a brick pit for tan or earth 

 in the centre of the house. Into this pit the pots 

 were generally plunged ; but sometimes the bed was 

 covered with a slate on which the pots were set. The 

 pots were also occasionally set on brick flues. Now, 

 when there is a pit in the centre, it is generally 

 covered with brick, and either contains tanks of hot 

 water, or hot water pipes, or flues. Sometimes it is a 

 hot air-chamber, furnished with gratings that can be 

 closed by slides, so that hot air can be admitted into 

 the house at pleasure ; observing that whenever hot 

 air is admitted into a plant house, by the Polmaise, or 



any other mode of heating, there must be open tanks or cisterns introduced 

 to give moisture to the air. There should also always be two or three ven- 

 tilators, or more, as near the roof as possible, to let off the air that has passed 

 through the house ; and if these ventilators are only of moderate size, there 

 is no danger of any cold air entering by them ; as the volume of hot air which 

 is continually rising to the roof, will either be sufficient to repel the cold air, 

 or at least it will mix with it, and warm it sufficiently to prevent any danger 

 resulting to the plants. 



544. The dry stove only differs from the moist stove in having less mois- 

 ture, as it is intended for the growth of the cactacse, and other succulent plants. 

 In some cases there is a kind of stage for the pots, like a green-house ; but 

 generally they are kept on shelves and flues. 



545. The aquarium. — This kind of house is more rare than any other, as 



^^^ 



