134 PLANT WORLD. 



the stomata. With the substantial help of the Botanical 

 Society of America and of the Carnegie Institution of Wash- 

 ington, it was possible to carry on this study in the desert 

 near Tucson, Ariz., at the Desert Botanical Laboratory. The 

 results of the work, which extended over the major portion 

 of three years have been published /'// extcuso as Publication 

 No. 82, of the Carnegie Institution of Washington. A brief 

 account of certain of these results will here be given. 



If it is true that stomata regulate transpiration, we 

 should expect to find that the opening of the stoma would 

 result in an increase in the amount of transpiration; and 

 contrariwise, a closure, apart from complete shutting which 

 scarcely occurs, would be accompanied by a decrease in trans- 

 piration. At a given degree of opening we should find a 

 constant amount of vapor loss. At maximum opening, a 

 constant maximum of transpiration should occur. It is only 

 if these be facts that anything like regulation may be recog- 

 nized to occur. To find the truth, it is necessary to be able 

 to determine the rate of transpiration and the size of the 

 stomatal openings independently at the same instant of time. 

 It is obvious that we may neither judge the rate of trans- 

 piration from the size of the openings, nor the size of the 

 openings from the rate of transpiration. How to do this 

 was the difficult task, but with a sufficiently small error, this 

 was done in the following manner: 



It was found that the stomata of certain, and probably 

 many, plants may be fixed in the form in which they are 

 found in life by tearing off the epidermis and plunging it into 

 absolute alcohol. The distortion of the stomata caused by 

 the tearing is only temporary, the guard cells recovering 

 their form just as a rubber ball does when it has been re- 

 leased from pressure. The alcohol extracts the water from 

 the cell-walls, thus rendering them rigid, and this it does 

 so rapidly that they do not have a chance to lose the water 

 contained within the protoplast while the walls are still 

 pliable, a process which would result in closure. 



