PERSPIRATION OF PLANTS. I* 



surfaces of the leaves ; but the upper surface of 

 perennial plants is seldom furnished with them ; 

 nor was I able to discover them on the inner sur- 

 face of the calyx of the red lily, but the lower 

 and outer one of these parts was constantly sup- 

 plied with thevn. 1 'hey appear in great abundance 

 upon the whole exposed surface of all leafless suc- 

 culent plants from warmer climates. 



The number of these organs in a given space of 

 a leaf may easily be found out ; for as the real 

 size of each of the represented particles was ^' T of 

 a square line, and as that of the red lily (Fig. 3.) 

 contains thirteen and a half of these apertures, we 

 may calculate from this, that their number in a 

 square line will amount to about $jj. From this 

 calculation, an idea may be formed of the prodi- 

 gious number existing in the total of the leaves of 

 a plant ; particularly when both surfaces are pro- 

 vided with them. 



That there must alfo be a difference with re- 

 spect to their number and size, according to the 

 different vegetables and the different parts of 

 the same plant, requires no demonitration, but 



v 



