OF ATMOSPHERICAL MOISTURE. 125 



their blossoms and young seed-vessels are destroyed 

 by frost, and their produce will retain its proper 

 flavour, which is always taken away by mildew. 

 {Hort. Tram., ii. ST.") 



CHAPTEE III. 



OP ATMOSPHERICAL MOISTURE AND TEM- 

 PERATURE.* 



The constituent parts of the atmosphere that sur- 

 rounds us are either the same in different regions, or 

 the differences, if any, are not appreciable by chemi- 

 cal processes. It is far otherwise as regards temper- 

 ature and humidity, which are so intimately con- 

 nected that they cannot be considered apart from 

 each other. 



From what has been already stated (Book I. Chap. 

 IV.), it is apparent that of the vital functions of 

 plants none are more important than those of perspi- 

 ration and evaporation; and that, while a certain 

 amount of loss of their fluid particles is necessary, a 

 great excess or diminution of the loss must be inju- 

 rious. Although the solar rays appear to be the 



* This subject has already been fully treated by Professor DanieU, 

 in his excellent paper, "On Climate with regard to Horticulture," 

 published in the Transactions of the Horticultural Society, vol vi. 

 p. 1. It is impossible for any one to discuss the same topic without 

 profiting largely by this important treatise, which I have very much 

 followed in the present chapter. 



