22 LIVINGSTON—ESTABROOK : STOMATAL MOVEMENT IN PLANTS 
their openings from day to night, though to a relatively slight 
degree. The diffusive capacity at night is about 12/16 (75 per 
cent) of its day magnitude for the upper leaf surface, and 11/15 
(73.3 per cent) for the lower. Furthermore, Eichhornia possesses 
by far the largest daylight openings with which we have dealt. 
Next in order are Allium with an open capacity about half as 
great as in Eichhornia, and Oenothera with an open capacity some- 
what less than that of Alium. Funkia and IJsatis are not widely 
different from each other in the diffusive capacity of their open 
stomata, which is approximately half as great as that of Allium. 
A comparison of the amount and rate of stomatal closure, as 
exhibited by the two sides of the leaf, indicates that the upper 
stomata close and open more rapidly, or close more completely, 
than do the lower, though this difference is not pronounced in 
Eichhornia. 
Many other points of interest are suggested by the data of 
TABLE II, but the time is not ripe for more detailed discussion; 
our aim in presenting these results has been merely to make a 
beginning in the acquisition of information upon which somewhat 
critical and quantitative studies may be based. It is hoped that 
others will attack this problem, so that the theory of stomatal 
effects may, as soon as may be, be brought to rest upon a more 
adequate foundation of actual’measurements than is at present 
the case. 
LABORATORY OF EXPERIMENTAL EVOLUTION, 
JOHNS Hopkins UNIversiry. 
