14 FRANCIS E. LLOYD 



more upon surrounding physical conditions than upon the stomata. 

 If, on the other hand, we accept the data as they stand, the role 

 of the stomata in regulating the leaf-water is still more negatived. 



CONCLUSIONS 



Comparative volumetric and gravimetric data show that in 

 the ocotillo, the ratio between the intake and outgo of water is 

 not a constant, but that the outgo during the day is greater than 

 the intake. The reverse relation obtains during the night. 



The amount of water relative to the dry weight of the leaves 

 decreases till noon or sometime thereafter, and then increases 

 till 4 a.m., approximately. 



The change in water-content of the leaf explains, in part at 

 least, the discrepancy between the income and outgo of water. 



The decrease of water in the leaf occurs during the opening of 

 the stomata. These organs are, therefore, not closely regulatory 

 of the loss of water from the leaf and are ineffectual in maintaining 

 a constant supply of leaf-water. Transpiration is, therefore, at 

 times too great, and the stomata do not serve to reduce it by clos- 

 ing movements; they may, however, limit it in a purely passive 

 manner. 



