142 PRINCIPLES OF GARDENING. [CH. IV. 



has well illustrated this by showing, that if the tem- 

 perature of a hot-house be raised only five degrees, 

 viz. from 75° to 80'', whilst the air within it retains 

 the same degree of moisture, a plant that, in the 

 lower temperature exhaled 57 grains of moisture, 

 would, in the higher temperature, exhale 120 grains 

 in the same space of time. 



Plants, however, like animals, can bear a higher 

 temperature in diy air, than they can in air charged 

 with vapour ; animals are scalded in the latter, if the 

 temperatiure is veiy elevated ; and plants die under 

 similar circumstances as if boiled. MM. Edwards 

 and Colins found kidney beans sustained no injury 

 when the air was dry at a temperature of 167" ; but 

 they died in a few minutes if the air was moist. 

 Other plants, under similar circumstances, would 

 perish, probably, at a much lower temperature ; and 

 the fact affords a warning to the gardener to have 

 the atmosphere in his stoves very dry, whenever he 

 wishes to elevate their temperatui'e for the destruc- 

 tion of insects or other pui'poses. 



Though growing plants can bear an elevated tem- 

 perature without injury, a very different effect is 

 produced upon them by even a lower heat, after they 

 have been separated from their roots. This has to 

 be borne in miud in the diying of potherbs, which, 

 though it is a process very simple and veiy important 

 for the winter's cuisine that it should be conducted 



