LIVINGSTON—ESTABROOK : STOMATAL MOVEMENT IN PLANTS 17 
TABLE [ 
Allium Cepa 
August 30, 3:00 p. m, August 37, 12:30 a. m. 
Dimensions of openings, i i i 
es Nab ci yageste Malaria Nab 
(axé) 
15 X4.2 7-94 
is XO 9.49 12.6 X3 6.15 
15 x6 9.49 12 X4.5 7:35 
15 XG 9.49 Remainder 
15°: XG 9.49 closed 
15 5-7 9.25 
I4.I X4.2 7.70 
I5 X4.2 7-94 
15 X3.6 7-35 
13.5 X3.9 7.26 
12.9 X4.2 7.36 
12.90 X4.5 7.62 
13358 XO 8.90 
14.1 X4.5 7.97 
18. X<3.9 8.38 
12.6 X4.8 7.78 
{5 x0 9.49 
12.90 X4.5 7.62 
x6 9-49 
12.9 5.1 8.11 
Mean Vab (the index of ahi: Mean V ab (the index of relative 
diffusive capacity) is 8.40. diffusive capacity) is 0.685. 
of the stomatal pore). These are expressed in the form of an 
indicated product. In the second column of each series is shown 
the square root obtained, in each case, from the product of a and 
b. If we assume that the stomatal pore is elliptical in cross 
section, then the derived square root must represent the diameter 
of a circle with area equivalent to that of the ellipse in question. 
If minute elliptical openings allow the passage of diffusing gases 
at approximately the same rate as do circular openings of the 
same cross sectional area,* and also if such rates of gas diffusion 
through minute circular openings are proportional, not to cross 
sectional areas but to similar linear dimensions (as the diameters) 
of the openings;{ then it follows that the square roots given in the 
* Brown, H. T., and Escomb, I. Static diffusion of gases and liquids in relation 
to the assimilation of carbon and translocation in plants. Phil. Trans. Roy. Soc 
London 193: 283-291. 1900. 
Stefan, J. Versuche iiber die Verdunstung. Sitzber. K. Akad. Wiss. Wien, 
math. nat. K!. 68: 385-428. 1873. This contribution formed the point of departure 
for the work of Brown and Escomb (loc. cit.). See also, on this subject, Renner 
(loc. cit.). 
