Vol. 33 



No 7 



BULLETIN 



OF THE 



TORREY BOTANICAL CLUB 



JULY, 1906 



Absorption of atmospheric moisture by desert shrubs 



Voi.ney Morgan Spalding 



A large body of more or less conflicting literature has accu- 

 mulated on the subject of the absorption of water directly from 

 the atmosphere by leaves and other aerial parts of plants. The 

 lack of agreement on this subject, and the fact that desert plants, 

 if any, might be expected to take advantage of this means of 

 adding to their meager water supply, led to an investigation of 

 this subject by the writer, the results of which have appeared in the 

 Botanical Gazette.* Briefly stated, they go to show that certain 

 desert shrubs absorb to a limited extent water that is presented to 

 their leaves and other aerial parts, while others under similar con- 

 ditions are quite incapable of doing so. 



At the time the experiments referred to were in progress no 

 attempt was made to determine whether any of these plants are 

 capable of absorbing water vapor directly from the atmosphere. 

 It was thought that the low relative humidity of the region in 

 which the Desert Botanical Laboratory is situated rendered such 

 a process improbable, or, if it occurred, that it could hardly reach 

 significant proportions. On returning to the laboratory, however, 

 in the fall of 1905, it was learned that the ocotillo, Fouquieria 

 splendens % a shrub which exhibits extreme sensitiveness to varia- 

 tions in water supply, and ordinarily casts its leaves in time of 

 drouth, had been in full leaf during the entire summer, notwith- 

 standing the exceptionally slight rainfall, the effects of which were 



* SPALDING, V. M. Biological relations of desert shrubs. II. Absorption of 

 water by leaves. Bot. Gaz. 41 : 262-282. 1906. 



[The BULLETIN for June 1906 (33: 327-365,//. /6, 77) was issued 20 J] 1906.] 



367 



