By John Frederic Daniell, Esq. 21 



same source. The Nepenthes distillatoria lays up a store of 

 water in the cup formed at the end of its leaves, which is 

 probably secreted from the air, and applied to the exigencies 

 of the plant when exposed to drought, and the quantity, 

 which is known to vary in the hot-house, is no doubt con- 

 nected with the state of moisture of the atmosphere. 



These considerations must be sufficient, I imagine, to place 

 in a strong light the necessity of a strict attention to the 

 atmosphere of vapour in our artificial climates, and to enforce 

 as absolute an imitation as possible of the example of nature. 

 The means of effecting this is the next object of our enquiry. 



Tropical plants require to be watered at the root with 

 great caution, and it is impossible that a sufficient supply of 

 vapour can be kept up from this source alone. There can 

 however be no difficulty in keeping the floor of the house, 

 and the flues continually wet, and an atmosphere of great 

 elasticity may thus be maintained in a way perfectly analogous 

 to the natural process. Where steam is employed as the 

 means of communicating heat, an occasional injection of it 

 into the air may also be had recourse to : but this method 

 would require much attention on the part of the superin- 

 tendant, whereas the first cannot easily be carried to excess. 



It is true that damp air or floating moisture of long con- 

 tinuance would also be detrimental to the health of the plants, 

 for it is absolutely necessary that the process of transpiration 

 should proceed ; but there is no danger that the high tempera- 

 ture of the hot-house should ever attain the point of saturation 

 by spontaneous evaporation. The temperature of the external 

 air will always keep down the force of the vapour ; for as in 

 the natural atmosphere the dew-point at the surface of the 



