THE EPIDERMAL SYSTEM. 



10:5 



(d) In the plants he examined he found that there were 



54 species with from 1 to 100 stomata per sq. mm. 



100 to 200 



aootoaoo 

 300 to 400 



400 to 500 

 500 to 600 

 600 to 700 



= 645 to 64.500 per sq. inch 



= 64,000 to 129,01)0 " 



= 129,000 to 193,500 " 



= 193,500 to 258,000 " 



= 258,000 to 322,500 " " 



= 387,000 to 451,500 



(e) Morren's measurements* vary somewhat from those given by 

 Weiss. The following, not given by Weiss, are taken from Morren's 

 table: 



In one square millimetre. In one square inch. 



(/) The stomata of the so-called Compass Plant (SUphium lacinia- 

 tum) are nearly equal in number on the two sides of the vertical leaves ; 

 there are on the true upper surface 82 per sq. mm. (= 52,700 per sq. 

 inch), and on the under surface, 87 per sq. mm. (= 57,300 per sq. 

 inch).f 



(g) On most leaves the Btomata are not distributed equally over all 

 portions of either surface ; they are not found on the veins, but are 

 restricted to the areas between them. In some plants this restriction 

 is accompanied by a further modification, as in Geanothus prostratus, 

 where the stomata are confined to the bottoms of sunken pits which 

 occur on the under side of the leaves. In the long harsh leaves of 

 Stipa spartea the stnmata of the upper surface are restricted to the 

 sides of the deep longitudinal channels which lie between the promi- 

 nent nerves. (See Figs. 135-6, pa<je 158.) 



* Published first in Bul'etin de V Academic royale de Bdgique, vol. 

 16, number 12, 1864, and also in part in Pringshehn's " Jahrbiicher," 

 etc.. 1. c. 



f See an article in American Xaturalist, 1877, p. 486 : " Observations 

 on Silphium laciniatum, the so-called Compass Plant," by C. E. Bessey. 



