118 BOTANICAL GAZETTE 
the guard cell. From these two considerations it would appear 
ful whether the guard cells move at all in either direction. Of co 
the glycerin experiment was repeatedly tried, but no motion 
discernible. The only other cells which by contact with the guard. 
can move them are the parenchyma cells whose processes push 
the guard cells on the under side. It was at first thought | 
parenchyma cells were operated by variations in turgescence 
epidermal cell, so that regarding the guard cells as immo 
not been experimentally proven by the glycerin test. Num 
instances were investigated carefully, but in not a single case di 
of the processes change their position. It is here confessed th 
reaction was noticed in any part of the stoma or adjacent 
Tesponse to the action of glycerin, nor was an instance found 
material where the guard cells appeared to be separated. 
experimental demonstration of the presence of a mechanism 
stomata, therefore, has not thus far met with success. 
are to be considered attempts on the part of the plant to close 
stomata permanently. It may be that not all the processes 
reach the center of the stoma and close it, so that, granted 
small opening exists between the guard cells, the number of func 
stomata would merely be reduced. The total number of 
per square millimeter was ascertained and found to be relatively s 
The estimate was made by counting the number of stomata 1 
section of serial sections taken from a portion of leaf of known %@ 
For instance, a piece of leaf 3™" long contained 52 stomata. 
lating the surface from the circumference of the cross section, 
would be 7 per square millimeter, or, in round numbers, 
square inch, oe 
It must of course be taken into consideration that sections 
leaves were used for experiment and not entire ones. If vat . 
