92 



Plant Physiology 



LEAVES WITH MORE STOMATA ON UPPER SURFACES 



54. The effects of conditions upon stomatal production. 



- It has been indicated that the preceding data are sug- 

 gestive. They do not, however, represent absolute rela- 

 tions, for the reason that the number of stomata is to a 

 certain extent a factor of complex environmental condi- 

 tions, varying with moisture-content of air or soil, light, 

 temperature, and other conditions. In this connection 

 some previously unpublished data 1 for corn and wheat 

 grown under conditions similar except as to moisture-con- 

 tent of the soil may serve as an illustration. The plants 

 were grown in tumblers of fine sand for seventeen days, 

 and the counts of stomata are averages for the microscopic 

 field employed (8 x ocular and 16 mm. objective). 



1 These data are the results of experiments made by Mr. F. M. Harris 

 in my laboratory. 



