DEPARTMENT OF BOTANICAL RESEARCH * 



D. T. MacDougal, Director. 



Progress in modern botanical science necessitates the correlation of a wide 

 range of phenomena interlocking with the activities of plants, and the devel- 

 opment of the main researches that have been taken up by the Department 

 has been much like the building of cantilever bridges, the farther ends of 

 which might come to rest upon piers in chemistry, physics, geology, or 

 geography. The chief problems of the Department have been taken to lie in 

 the domain of phyto-chemistry, in the water-relations of plants, and in the 

 environic reactions of organisms. The development of methods and the 

 broader interpretation of the results have extended far into the field of 

 conjunctive science, and have led to the consideration of some physical, 

 biological, and meteorological subjects, not usually included within the prov- 

 ince of botany, but which are of the greatest importance in the geographical 

 aspects of the subject. Thus it became apparent, early in the studies of the 

 Salton lake, that the revegetation of the beaches emersed each year varied 

 progressively, but more widely than justified by the simple concentration of 

 the water. Next bacteriological examinations by Dr. Brannon showed that 

 "sulphur" bacteria found in the neighborhood of decaying submerged trees 

 were breaking up the sulphates and that deposition of calcium as a carbonate 

 ensued. The removal of the calcium from the water unmasked the sodium 

 in the form of common salt in such manner that it exerted a much greater 

 toxic action on the plants and seeds with which it came into contact. 



Another generalization of importance is that of the "equation of the 

 desert" or index of aridity, constructed on experimental and instrumental 

 evidence by Dr. Shreve, in which the ratio of evaporating power of the air 



to the soil-moisture into the time (^rv,x t\ is found to express graphically 



and accurately the relative aridity of any region. Thus the Desert Labora- 

 tor}' domain (2,300 feet) is 30 times as arid as the montane plantation (8,000 

 feet) in the near-by mountains. 



THE CAHUILA BASIN. 



THE MAKING AND DESICCATION OF SALTON LAKE. 



The results obtained from the studies made by various collaborators upon 

 the phenomena consequent upon the formation of Salton Lake in the Cahuila 

 basin will be presented in a manuscript to be completed at the end of 191 2. 

 The combined observations of the workers engaged with this subject extend 

 over a period of 59 years, beginning with the original discovery of the fact 



* Situated at Tucson, Arizona. Grant No. 741. $37,905 for investigations and main- 

 tenance during 1912. (For previous reports see Year Books Nos. 2-10.) 



4— YB 49 



