TME EPIDERMAL STBTEM. 



103 



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



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



38 " " 100 to 200 



S9 " " 200 to 300 



12 " " 300 to 400 " " 



9 " " 400 to 500 " " 



1 " " 500 to 600 " " 



3 " " 600 to 700 " 



= 645 to 64,600 per eq. inch 



= 64,500 to 129,01)0 " 



= 129,000 to 193,600 " 



= 193,500 to 258,000 " 



= 258,000 to 322,600 " 



= 322,500 to 387,000 " 



= 387,000 to 451,500 " 



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

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

 table : 



(/) 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. (= 53,700 per sq. 

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

 inch).-)- 



{g) On most lea-ves the stomata 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 Geanoi7ius prostratus, 

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

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

 B,ipa spartea the stomata of the upper surface are restricted to tlie 

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

 nent nerves. (See Figs. 135-6, page 158.) 



* Published first in Bvl'etin de VAeademie royals de BeHgique, vol. 

 16, number 13, 1864, and also in part in Pringaheim's " Jahrbilcher," 

 etc., 1. c. 



t See an article in American Naturalist, 1877, p. 486 : " Observations 

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



