PERSPIRATION OF LEAVES. 18? 



perspiration, but all proving it to be con- 

 siderable. Evergreens are found to perspire 

 much less than other shrubs. 



The state of the atmosphere has a great 

 effect on the rapidity of this perspiration. 

 Practical botanists know how much sooner 

 plants fade, and haymakers experience how 

 much faster their work is done, some days 

 than others, and those days are by no means 

 always the most sunny. In a hot dry day 

 plants are often exhausted, so as to droop 

 very much towards evening, especially in the 

 dry unsheltered bed of a garden. Such as 

 have fleshy roots, indeed, have a singular 

 power of resisting drought, which has already 

 been explained p. 113. Succulent plants, 

 destined to inhabit sunny rocks, or sandy 

 deserts, imbibe with the greatest facility, 

 and perspire very sparingly. Evergreens are 

 not generally very succulent, but their cuti- 

 cle appears to be constructed like that of 

 succulent plants, so as to allow of little eva- 

 poration. The Cornelian Cherry, whose im- 

 mense perspiration we have recorded, p. 0'8, 

 has a thin dry leaf, capable of holding very 

 little moisture. 



