DEPARTMENT OF BOTANICAL RESEARCH* 



D. T. MacDougal, Director. 



The resources of the Department and the energy of the staff members 

 have been devoted to the furtherance of the investigations outlined in the 

 report of the preceding year. Substantial progress has been made in the 

 accumulation of data for the development of better-founded generalizations 

 upon all of the problems under consideration. The direct results of such 

 work ma_v be best presented in memoirs dealing with completed researches. 

 Isolated groups of facts and minor generalizations incidental to the main 

 problems are constantly coming to light, however, and these may be most 

 suitably dealt with in briefer articles in various technical and non-technical 

 journals. The editors of such periodicals have been uniformly courteous and 

 prompt in the acceptance and publication of contributions of this character. 

 This may be reckoned as one of the most valuable forms of cooperation ren- 

 dered the Institution, and greatly increases its facilities for publication. 



THE ADVANCE AND RECESSION OF VEGETATION IN THE DEPRESSED 

 BASINS OF THE COLORADO DELTA. 



The actual beginning of the study of the movements of vegetation in the 

 Salton and Pattie basins has necessitated a preliminary survey of the areas 

 under consideration. An expedition for this purpose was assembled at 

 Mecca, California, February 5, 1907, and embarked in a sailboat designed 

 and constructed by Mr. G. Sykes, for the circumnavigation of the Salton Sea 

 and an examination of its contacts with the contiguous desert vegetation. 

 The main inflow from the Colorado River was closed while the expedition 

 was afloat, and the maximum level was attained on February 10 or 11, when 

 the area of the lake was estimated as about 500 square miles. (See plate 2.) 



Six sections of shore formation were selected as bases from which the 

 succession of vegetation will be followed as the water recedes toward the 

 bottom of the basin. The greatest depth of water found by soundings was 

 84 feet, and the greater part of the lake will probably disappear in 10 years. 

 As the area occupied by the water is from 5 to 25 miles in width, it may be 

 seen that stretches of beach from a few hundred yards to 2 or 3 miles in extent 

 may become available for occupation by plants during a single season. 



Observational area No. i comprises a gentle slope of loam, which contained 

 over 3 per cent of alkaline salts, and bore principally Allcnrolfia and Sueda, 

 near Old Beach, on the northeastern shore of the lake (plate 3). No. 2 



* Situated at Tucson, Arizona. Grant No. 399. $25,000 for investigations and main- 

 tenance. (For previous reports see Year Book No. 2, p. xxvi; Year Book No. 3, pp. 

 98-100; Year Book No. 4, pp. 126, 127; Year Book No. 5, pp. II9-I35-) 



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