season, the amount of precipitation being one and one-tenth inches 

 within two liours, drenching, of course, all the vegetation. On 

 the following day (the 12th) at four P. M., it was quite evident to 

 the eye that the buds had made a start. By July 13, the slender 

 conical buds along the whole extent of the stems were 7 to 8 milli- 

 meters long. On July 14 at five A. M., the rosettes of leaves 

 were well formed; the length of the largest leaves was 1.5 centi- 



FiG. I. Fouquieria splmdens, showing a branch which had been irrigated during 

 four days. 



meters, their size being, however, quite uniform. On July 15, 

 the photograph forming the second figure was taken. It will be 

 noted that the leaves on the irrigated stem were at that time much 

 larger than the freshly formed leaves, that is, those produced after 

 the rain, and as a result of the stimulus thereby given. 



It will be noted that the development after the rain was more 

 rapid than after irrigation, notwithstanding that the water was 

 applied artifically from time to time during the period of growth 

 under observation, while the wetting by rain occurred but once. 

 The fact, however, must not be lost sight of, that following the 

 rain there is a marked rise in the relative humiditv, though I re- 



