1918] BAKKE—WILTING 105 
menting upon Fittinc’s (19) work upon the osmotic pressure 
present in desert plants, makes the statement that with the 
lowering of the vapor tension 10 per cent there is represented a 
pressure of 100 atmospheres. In an examination of the graph in 
table I there is a reduction in the index from 0.92 to 0.19 during 
the process of wilting. This therefore represents an approximate 
pressure of 800 atmospheres. For plant B there would be an 
approximate pressure of 700 atmospheres. Table V and fig. 4 
give leaf Ia, as being able to withstand a pressure of 666 atmos- ~ 
pheres and leaf Ia, 860 atmospheres. Leaf Id,, with an index o. 10, 
Suggests a pressure as high as goo atmospheres. At that time 
the margin of the leaf was sufficiently dry so that the clip could not 
_ be used without causing injury. This status becomes all the more 
pertinent when it is compared with the data submitted by SHULL 
(41), where the force present in air dry seed (Xanthium) is equiva- 
lent to 1000 atmospheres. 
During the daily march of foliar transpiring power there is 
usually considerable variation (figs. 2, 3), even when a plant is 
supplied with an optimum amount of water. The sudden rise in 
the foliar transpiring power immediately after sunrise, as set forth 
by Bakke and Livrincston, gives credence to the view that the 
stomata open quickly at this time. In using the porometer and 
Standardized cobalt paper squares simultaneously, TRELEASE 
and Livincston (42) find that during the daily march there is 
considerable agreement between the porometer readings and the 
readings of the foliar transpiring power by the method of stand- 
ardized cobalt chloride paper. From the results obtained in their 
investigation they concluded that the porometer gives readings 
which show the extent of stomatal diffusion. 
DARWIN (12, 13), using the horn hygroscope and the tempera- 
ture method, has shown that during wilting there is a temporary 
Opening of the stomata. Darwin and Prrrz (14), using the 
porometer, have demonstrated that a similar condition is present 
during wilting. Lamztow and Knicut (26) in their work upon 
stomatal behavior during wilting, where they employ a recording 
porometer, have confirmed the results of Darwin and PERTz, in 
that the stomata open temporarily during wilting. For Phaseolus 
