18 INTRODUCTION. 



begin to grow in winter or before the time usual 

 for increasing the appUcation of warmth and 

 moisture, they may be removed to the hotter 

 house, where the necessary stimuh will be in 

 waiting for them. 



In the case of very large collections, it would 

 indeed be advisable to provide even a third 

 structure, to be devoted to the species requiring 

 less warmth while dormant, such as those from 

 the elevated districts of America — this house 

 with the plants at rest might be kept with a tem- 

 perature as low as 45° or 50" during the day, and 

 at night it may even be lowered to 40°. With a 

 large number of these plants to grow, it would be a 

 far preferable arrangement to have three small, 

 rather than one or two large houses; and where a 

 general collection is grown, it is almost indispensa- 

 ble to have the Indian species, and those of the 

 hotter climates in a house by themselves, with a 

 temperature during the summer months ranging 

 from 70° to 80° without the aid of sun heat ; but 

 if raised by it as high as 90° no danger need be 

 apprehended, as air may be given more freely at 

 the roof of the house during the middle of the 

 day: and by doing so, the atmosphere of the 

 house will be rendered sweet and pure, and the 

 plants consequently benefited by it. At night 

 the temperature should fall as low as 65°; by re- 

 ducing it at night, I find that it causes moisture 



