1909] BERGEN—TRANSPIRATION IN YOUNG SEEDLINGS 277 
development were made on plants of Phaseolus. In different lots of 
these, the moist-air individuals were 15 to 40 per cent. taller than those 
grown in drier air. The leaves of the former were sometimes as 
much as 80 per cent. longer than those of the latter, the difference 
being largely in the petioles. On the other hand, the diameter of the 
first internode above the cotyledons was (in plants grown in the green- 
house) 30 per cent. greater for those outside the moist glass cases. 
For house-grown plants the leaf thickness was 25 to 40 per cent. 
greater in the dry-air plants, and for those grown in the greenhouse 
Fic. 2. Sinapis, entire stem and leaves, moist-air form. X4.—Fic. 3. Sinapis, 
upper half of stem and leaves, dry-air form. X 
it was 2 5 per cent. greater than for those under glass cases. The 
Most notable differences in growth of dry-air and moist-air individuals 
Were shown by Ipomoea, in which the moist-air specimens were 
‘wining freely, when dry-air specimens of the same age had relatively 
short internodes and showed no tendency to twine (fig. 1). Mirabilis 
Plants in nearly saturated air, by the time the second pair of true 
leaves had spread apart, were three times as tall as those grown in 
house air and much more slender. Sinapis, on the other hand, 
appears depauperate when grown in nearly saturated air, as shown 
% gs. 2, 3. The leaves of Sinapis, and of Cucumis also, in very 
Moist air often show the less indented margin referred to by WIESNER.* 
3 Wiesner, J., Biologie der Pflanzen 65, 66. Wien. 1902. 
