12 TRKATMENT OF EPIPHYTAL OECIIIDS. 



tliey are i=;ure to assume a brownish colour, wliich looks un- 

 healthy ; shading, however, should only be used during bright 

 sunshine, in summer, and autumn ; it should by no means be 

 kept on for the season, as is frequently the case; on the contrary, 

 it should be removed every afternoon to allow the plants the 

 uninterrupted light of the evenings and mornings when the sun 

 is not too powerful. 



The best sliading is strong canvas on rollers, which should be 

 made to unrol from the bottom of the roof upwards, for fre- 

 quently the lower portion of the house only requires to be 

 shaded. 



In glazing, all the laps should be made quite close, and large 

 squares of glass should be avoided ; at least wide ones, not only 

 on account of their being liable to breakage, but if the squares 

 are narrow less sliading is required. Tliere can be little doubt that 

 if an Orchid-house was glazed with rough plate-glass, shading 

 might be dispensed with altogether, or nearly so, and with 

 advantage to the plants. 



Night-covering on the outside of the house is very desirable 

 in winter ; this may easily be effected by placing a waterproof 

 kind of canvas on the rollers which are used for the shading. 

 The best way to prevent excessive dryness at night is to lower 

 the temperature produced by fire-heat as much as possible ; and 

 this can only be done with safety when some external covering is 

 used ; for the temperature of the glass in the roof of a hothouse 

 at night, when fully exposed, is exactly the mean of the external 

 and internal air, and consequently in very cold weather and 

 when there is moisture floating in the internal atmosphere, it 

 becomes a great condenser, and dries the air of the house much 

 faster than it otherwise would be. This an outer covering 

 prevents, in a great measure, and it also tends nmch to obviate 

 drip. 



The plan of having climbing plants trained over the roof is 

 objectionable, for in general the plants are too much confined, 

 receive too much moisture and heat, grow too luxuriantly, and 

 consequently seldom flower in perfection ; besides they require 

 much attention to keep them in order and to free them from 

 insects, and at certain times they produce too much shade. 



2. Atmosphere, Temperature, Sjc. 



The most obvious defects in the present management of Orchid- 

 houses consist in the want of attention to their atmosphere, 

 particularly as regards moisture, for the plants in such structures 

 derive the greater part of their subsistence from the vapour of 

 the house; much more, therefore, depends upon this point in 



