404 Cannon : Transpiration of Fouquieria 



surprising, and this phase of the plant's history constitutes one of 

 the most admirable of adaptations to desert conditions. 



Record of experiments 



All of the experiments on Fouquieria which are reported in 

 this paper, but which constitute a part only of those performed, 

 were conducted with the polymeter method oi determining trans- 

 piration already mentioned,* and all were conducted upon plants 

 or branches in place. It will only be necessary for the sake of 

 clearness to point out the significance of the figures under the 

 heading " Amount in milligrams." In each instance the first 

 number refers to the amount of moisture present in the bell-glass^ 

 which encloses the plant, at the beginning of the experiment ; the 

 second number is the amount of moisture in the bell-glass at the 

 end of the experiment. The difference between the two numbers 

 constitutes of course the amount transpired in the time expressed 

 in the first column. 



Transpiration of Fouquieria No, I. Experiments i-6 



Fouquieria No, I is growing about 150 meters south of the 



r 



laboratory building. It has half a dozen branches and is about 

 one-half a meter high. The first three experiments were per- 

 formed when the plant was leafless, because of the severe drought ; 



F 



leaves were present in the other experiments. 



Experiment No. /, February 12 : Transpiration of leafless steuis 

 The following data were derived from this experiment : 



lime. 



Per cent, of 

 saturation. 







Temperature. 



Amount m 

 milligrams. 



10:30 

 12:30 



23.5 



27 







78° F. 

 81 



65 

 68.5 





Experiment No. 



2, 



Feb) 



'uary ij : 



T/ie same 



Time. 



Per cent, of 

 saturation. 







Temperature. 



Amount in 

 milligrams. 



11:40 

 1:40 



28. s 

 3» 







77'' F. 

 79 



63.7 



73-7 



The rate of transpiration in Experiment No. l is 1.85 milli- 

 grams per hour; that in the succeeding experiment is 5 miHigrams 

 per hour. 



* Cannon, /. c, 



