LIVINGSTON—ESTABROOK : STOMATAL MOVEMENT IN PLANTs 19 
the calculated diffusive capacities, are given the minima, means, 
and maxima of the actual dimensions. These latter are expressed 
as a series of three quantities, the middle one, in full face type, being 
the mean. The two series thus given for each hour represent, 
of course, the two axes of the stomatal ellipse. The number of 
stomata per square millimeter of leaf surface is given above the 
data in each case, excepting that of Allium, where it was not 
determined. Funkia has stomata only below and Allium has but 
one leaf surface to be considered. 
It appears from our results that the diffusive capacity of the 
stomatal openings reached the zero point at night in all cases 
excepting Allium, Eichhornia, and the lower leaf surface of Oeno- 
thera. This is not to be taken as meaning even that stomatal 
transpiration actually ceased when the index of diffusive capacity, 
as here determined, vanished. There must always be some 
stomata that are SLIGHTLY open, and some diffusion undoubtedly 
may occur when closure is apparently complete. Of course, 
cuticular transpiration must continue whether the stomata are 
open or closed. 
The greatest diffusive capacities are exhibited by the aquatic 
Eichhornia, and the stomata of this plant are clearly seen to alter 
TABLE II 
Funkia 
Lower leaf surface (54 stomata per sq. mm.) 
Time of observation | ere 
Dimensions of openings, icra Index of relative diffusive 
capacity 
Aug. 30 | 
3:00 p. m. 0.6-0.5—3.0 
| 3-93 
10.0-I1.0-I5.0 
6:30 p. m, 0 Xo 0.00 
Aug. 31 
12:30 a. In: 0,0-0.2'7-3.0 
0.54 
0.0-1.0—-I1.4 
5:30 a.m. 0.0-1.08—4.5 
1.05 
0.0-3.6—15.0 
10:00 a. m. 0.0-1.3-3.0 
2.88 
0.0-6.5-15.0 
