154 



FIXED STRUCTURES FOR GROWING 



Fig. 124. 



about four and a half feet (* Gardener's Magazine,' vol. xiii. p. 15). 



There are, however, plant-houses erected not merely for growing 



plants, but for walking into, in 

 order to enjoy them ; and in 

 these, other considerations 

 interfere with rigid economy, 

 both in heating and lighting. 

 The form of plant-houses, 

 therefore, must be determined 

 by the object in view, and the 

 means at command. For early 

 and for late forcing, narrow 

 houses with upright glass, or 

 r^ glass at a very steep slope, are 

 ^- preferable, as giving but a 

 small volume of air to be heated, 

 and as admitting the sun's 



Lean-to vinery. ra 7 s at a ri g ht an g le > at those 



seasons when he is low in the 



heavens, and shines only for a short time. For summer forcing the 

 angle of the roof may be larger, and of course its slope less steep ; 

 for greenhouses and plant stoves, in which plants are to be grown all 

 the year, there should be a portion of the roof with the glass very steep, 

 or upright front glass, for admitting the sun's rays in winter. The 

 roofs of such houses may be at a large angle, say from 35 to 45 with 

 the horizon, which is more favourable for throwing off rain, and also 

 for resisting hail, than a flatter surface/ For growing herbaceous 

 plants and young plants, and for the general purposes of propagation, 

 whether by seeds, cuttings, or layers, a low flat house, in which the 

 glass shall be near to all the plants, as in pits and frames, is the most 

 Fig. 125. convenient form ; though when fruits are to be 



ripened in such houses in the winter season, the 

 flatness of the glass, and consequent obliquity 

 of the sun's rays to it, is a great disadvantage. 

 Hence, when such plants can be conveniently 

 grown in pots, as in the case of strawberries, 

 or bulbous or other flowers, it is desirable to 

 have very steep glass, and to place the plants 

 on shelves immediately within it, as practised by 

 Mr. Wilmot, and other market-gardeners, in such 

 structures as fig. 125 -, or, when the plants are 

 climbers, as the cucumber and melon, to train 

 them up trellises parallel to the glass, and at a 

 short distance within it, as in Ayres' cucumber- 

 house. 



Steep-roofed house for Curvilinear roofs. The ordinary form of the 

 winter forcing of plants roofs of plant-houses is that of a right-lined 

 fapot*- plane, like the roof of any other building, but 



they have been also formed with curvilinear roofs, which, as compared 



