44 
THE FLORIST’S JOURNAL. 
the surface of the glass ; and the nearer the inclination of the 
roof is to the horizon, so much more the light is refracted, and 
the more decomposition takes place—a nearly flat roof throwing 
the light obliquely on the back wall of the house, and not allowing 
it to descend to the stage or pit in the centre of the house till it is 
reflected back from the wall. On the other hand, a snarp pitch 
will allow it to fall in almost direct rays upon the plants in the 
body of the house; so that it may be readily inferred that the 
inclination of the roof is of much consequence, and should be 
arranged to accord with the character of the plants to be grown 
under it, the angle being such as to allow them to receive the 
light in direct lines, at the time of their greatest perfection. 
Thus, for such collections as are usual to greenhouses, being of 
a miscellaneous character, many of them blooming at an early 
period in spring, and again in the autumn, an angle of 45 degrees 
is best suited, in order to catch the sun s rays while that body is 
yet low in the horizon ; and most of the plants being removed 
to the open air during the summer months, they do not suffer 
from over-heating at that time; but if the house is devoted to 
either Geraniums or Ericas, a lower inclination is required. Their 
blooming season occurring at a later period, an angle of 40°, 
considering the ground line as the base, is better for them. If 
the erection is designed for Cacti, the slope of the roof cannot 
well be too sharp, as they delight in a flood of strong light. On 
the contrary, for Orchidaceous plants, and those of similar habit, 
a less inclination, say of about 35°, is fully sufficient. 
The form of the roof, also, affects the plants growing under it 
to a considerable extent, as it is more or less capable of admit¬ 
ting light, and maintaining an equable temperature,—the old 
a lean-to” roofs are fast giving way to the span and curvilinear. 
In our estimation nothing equals a short span roof, no higher 
than is positively necessary to afford head room to the plants 
under it, and this plan admits of very superior ventilation. , A 
curved roof has a light and pleasing appearance, but is generally 
deficient in this latter requisite—and if one point be more im¬ 
portant than another it is the admission of air—a blaze of light 
and a free current of atmospheric air being equally necessary 
and required at the same time. And in a due provision for ven- 
