1909] | BERGEN—TRANSPIRATION IN YOUNG SEEDLINGS 279 
dry house air. Bits of the lower epidermis were peeled from the 
under surface of each kind of leaf at about 2-minute intervals and 
instantly placed in absolute alcohol to fix the stomata.’ The opera- 
tion was repeated on another day with fresh sets of leaves. It was 
found that in less than six minutes the stomata of the dry-air leaves 
were most of them closed to less than half their initial width, while 
; Fic. 4. Nicotiana leaves; A, moist-air form; B, dry-air form. X4.—Fic. 5. 
Pomoea leaves; A, moist-air form; B, dry-air form. X4 
those of the moist-air leaves were but little affected. In about 15 
minutes most of the stomata of the dry-air leaves were tightly closed, 
While most of those of the moist-air leaves still remained open. 
_ Apparently the speedy wilting of the moist-air leaves is due to two 
causes, the insufficient closure of the stomata and the relatively high 
Permeability of the general surface of the epidermis to moisture. 
Wag vto™ F. E., The physiology ‘of stomata. Publ. 82, Carnegie Institution of 
ashington, 1908, 
