456 BOTANICAL GAZETTE [JUNE 
especially STAHL (47), is an important factor in reducing tran- 
spiration at that season, when the water intake is at best very low. 
The work of Lioyp (32) on Fouquieria led him to conclude that the 
capacity of the diffusion of the stomates was well in excess of 
what would be required for the greatest observed transpiration 
rate. F. Darwin (DELF 15), in a preliminary account before the 
British Association, concluded that if the stomates can be observed 
by a sufficiently delicate method, the stomal movements will be 
found to correspond closely with changes in the rate of transpiration 
caused by alteration in external conditions. 
In the present investigation, in which the method of relative 
time of penetration of an oil was used to indicate the condition of 
the stomates, there was no evidence that the stomates exercised 
“closely regulatory” function. The stomates opened in the 
morning, in general in the diffused light of dawn, but the rate of 
transpiration showed no sudden rise, but rather kept proportional 
to that of the evaporating power of the air. In the afternoon the 
stomates did not begin to close until after the beginning of the 
decline in transpiration. This was true both in potted plants and 
in cuttings properly cared for on days that were not extreme. In 
many cuttings the closure of the stomates seemed to be due to the 
shock of cutting rather than to any excessive water loss. Almost 
all of the wilted plants had their stomates closed, but in dried 
leaves the stomates were open. 
The experimentation on plants in the field led to the conclusion 
that the stomates were open during the hours of sunshine, and that, 
although the opening of the stomates preceded the rise in tran- 
spiration in the morning, the decline in transpiration set in in the 
afternoon before the beginning of closing of the stomates. The 
rate of transpiration sank more quickly to a lower level than the 
time it took the stomates to close could possibly account for. 
Experimentation 
MATERIALS AND METHODS? 
Throughout the study of this problem an experimental method 
was used which yielded numerical data. The experiments were 
carried on upon bog plants, principally: Chamaedaphne cane 
2 Cf. BURGERSTEIN 3. 
