Cannon: Transpiration of Fouquieria 411 



on March 26 and 28 about 20 gallons were put slowly on the 

 ground at its base. As a result leaves were put out very promptly 

 and the total transpiration was increased many fold. 



T^"^«- ^amrl'Jio/ Temperature. ^Jf}*'""^ *" 



saturation. ^ milligrams. 



10:03 28 26° C. 133.7 



10:13 72 27 382.5 



The rate of transpiration is 1492.8 milligrams per hour for the 

 entire plant. 



The history of the leaf-covering of Fouquieria No. II from 

 February to August is of interest. The plant was seen to be in 

 leaf the latter part of February, but as a result of the long drought 

 in March the leaves fell away, so that the foliage which the plant 

 formed the first part of April after it had been irrigated (Experi- 

 ment No, 8) was the second leaf-covering of the year. April was 

 a dry month and the plant was again defoliated. The drought was 

 broken by a rain about the middle of May and Fouquieria No. II 

 came into leaf for the third time. With the advent of dry and hot 

 weather in June the leaves fell away again. On June 29 three 

 gallons of water were poured slowly on the ground at the base of 



the plant. 



July I, and at 2 P. M. on 



the succeeding day they were i cm. long. On the fifth the leaves 

 were of mature size. (Compare figure 6.) The leaves which 

 were formed at this time, during an extremely dry season (figure 

 2), soon withered and the plant was defoliated the fourth time. It 

 is of interest to note that with the coming of the summer rains 

 still another leaf-covering appeared on the plant, and therefore, it 

 happened that Fouquieria No, II came into leaf five separate times 

 between February and August, and that the exciting cause in each 

 instance was an increase in the available water-supply. 



Experiment No. p, April 6 and 7 ; Daily periodicity 



On the morning of April 6, at 9:53, the rate of transpiration of 

 Foitqidcria No, II was taken and it was observed at hourly inter- 

 vals throughout the day until 8:52 P. M. The experiment was 

 continued the following morning at 4:32 and readings were made 

 every hour until 8:20 A. M. The record of transpiration was com- 



