ii DEVELOPMENT AND ENVIRONMENT 39 



expressed doubts as 

 to the importance 

 of the stomata in 

 regulating transpir- 

 ation, but such is 

 certainly their 

 function in the 

 cotton plant. Con- 

 sequently, an ex- 

 amination of the 

 stomatal move- 

 ments, so far as 

 they are at present 

 known, is necessary 

 to an understand- 

 ing of the way in 

 which the stem 

 loses water. 



The stomata of 

 Egyptian cotton 

 plants are found 

 on both surfaces of 

 the cotyledons ; on 

 the hypocotyl and 

 stem, and on both 

 surfaces of the foli- 

 age leaves. 



A full-grown 

 stoma is about 0'04 

 mm. in length, and 

 the mean .fre- 

 quency of these 

 organs in each 

 square milli- 

 metre has been 

 found to be as 

 follows. 



- 144 cm. ' .- 

 below the surface 



i 



FIG. 38. REGENERATION 

 OF THE ROOT SYSTEM. 



200 cm. below 

 the surface 



Showing crop of new roots developed in six 

 weeks from merely one uninjured lateral (the 

 dotted line). Tracing from a blue-print of 

 the root itself, after floating it upon a sheet 

 of glass. See Fig. 35 and also 30. 



