Lioyp: LEAF WATER IN GOSSYPIUM | 13 
not obtained with a view primarily to obtaining light on the 
accumulation of carbohydrates, the general correspondence of the 
Alabama figures with those quoted may be noted. The greater 
efficiency of the Arizona plants possibly may be due to the fuller 
development of the leaves. This would be indicated by the 
performance of the old leaves on October 1 and 8 (series 6 
and g), which showed an increase of 30 and 26 per cent., but 
more surely, if it were not for the general irregularity of their 
behavior and the entire failure to get an increase at all in series 12 
and only a very slight one in series 5. On the other hand the 
light conditions in Arizona are much more favorable in view of the 
frequent cloudiness in Alabama. The days on which the Alabama 
material was collected were partially cloudy, while that from 
Arizona was taken on continuously clear days. 
The old leaves betray a much more erratic behavior and the 
data lead us to no safe conclusion. In the two cases, TABLE VI, 
series 5; TABLE VII, series 9, however, in which there was a 
marked increase in dry weight, there was also a marked re- 
covery of leaf water after the 10 hour. By contrast, however, 
the leaves that contained the greatest quantity of water, series 
12 of October 13, were the least efficient photosynthetically, a 
circumstance which throws doubt on the inference that the failure 
of the leaves of series 5, taken from all parts of the plants, to add 
to their dry weight after the 10 hour, was due to a marked loss 
of water during the corresponding period. 
STOMATAL MOVEMENT 
A glance at FIG. 2 will show that after the 10 hour has been 
reached there is a distinct tendency to recover the leaf water lost 
during the earlier hours. It is important to inquire whether this 
tendency, which begins to make itself evident during the part of 
the day when transpiration rates may be assumed to be the highest, 
is in correlation with the behavior of the stomata. 
Balls,* in Egypt, found by means of his newly devised stomato- 
graph that the stomata of the cotton slowly close as the hottest 
part of the day approaches, completing the closure as the sun 
passes behind neighboring trees at 13.40 hr., remaining closed all 
* Balls, W. L. The “Stomatograph.” Nature 87: 180. 10 Au 191t. 
