116 THE SALTON SEA. 



The effects of volcanism have furnished other opportunities for observation upon 

 the invasion of sterilized areas on the surfaces of cooled lava flows. The physical condi- 

 tions of the substratum are highly specialized under these circumstances, and moreover it 

 has been found difficult to make any definite analysis of the determining factors in the 

 movements of the vegetation appearing in such places, although some extremely interesting 

 records of these phenomena have been made. The most important and most recent work 

 upon this subject was done by C. N. Forbes, in the Hawaiian Islands.^ ( See Note below.) 



Newly made lands about the mouths of rivers generally furnish a substratum highly 

 favorable to the growth of a number of species of higher plants as soon as the deposition 

 reaches a stage where the surface is brought permanently above the level of the tide, and 

 the conditions are very favorable for observation of the successions.'' Such occupations of 

 bare soil by open formations and later by closed ones have also been described by Flahault 

 and Combes.' Newly made alluvial was first occupied by Salicornia macrostachya, fol- 

 lowed by Salicornia sarmentosa, Atriplex portulacoides, and Dadylis sarmentosa. As may 

 be seen from the contents of the present paper, the procedure on the emersed lands of the 

 Salton is widely different from that in any of the above cases. 



THE SALTON SINK. 



The Cahuilla Basin lies in the most arid part of North America, and although the 

 making of the lake in the Salton Sink or portion of the basin below sea-level may be finally 

 due to climatic factors, yet it is caused directly by overflow from the channel of the Colorado 

 River. The geological record seems to indicate that the Sink has been filled and dried out 

 at intervals over a long period extending up to the present time. Circumstantial evidence 

 points to the conclusion that hardly twenty years have passed without some inflow from 

 the river into the Sink, but the only available actual record of any other inundation besides 

 the one the effects of which are considered is that of the overflow of 1891, when the passage 

 from the river to the small lake formed in the Sink was made by a single man in a boat 

 on the inflowing current for the purpose of ascertaining the source of the water forming 

 the lake. (See p. 19.) (Plate 15.) 



The formation of the lake in 1905, 1906, and 1907 occurred under circumstances that 

 gave unexcelled opportunities for a study of the attendant phenomena. A number of 

 naturalists had visited the Sink in the half century following the Williamson expedition 

 through it (1853) and something of the nature of the surface formations as well as of the 

 plants and animals had become known. Furthermore, a short visit to the bottom of the 

 basin near the railway station of Salton had been made by Messrs F. V. Coville and D. T. 

 MacDougal in 1903, and a brief description was published as to the aspect of this part of 

 the Colorado Desert, including an area to the northwestward. Photographs of parts of the 

 Sink which were afterwards submerged were also obtained. * 



In 1904, an expedition from the New York Botanical Garden, in which Dr. D. T. 

 MacDougal, Mr. G. Sykes, and Prof. R. H. Forbes participated, started from Yuma in 

 February and went down the river through the Delta and to the western shore of the Gulf 

 of California.* One camp was made a short distance to the southward of the boundary 

 between the United States and Mexico, near an intake of an irrigation canal leading to 

 an area in the basin being brought under cultivation, and brush dams were seen extending 

 out into the stream for the purpose of forcing the current into these artificial channels. 



' Forbes, C. N., Plant invasions of lava flows. Occasional Papers, B. P. Bishop Museum, etc., vol. v, p. 244, 1912. 

 « Oliver, P. W., The Bouche d'Erquy. New Phytologist, vol. vi, pp. 244-252, 1907. 



• 8ur la flore de la Camargue et des alluvions du Rhone, Bull. d. 1. Soc. Botan. d. France, vol. xli, 1894. 



* See Coville and MacDougal, The Desert Botanical Laboratory of the Carnegie Institution, pp. 20-22. Publication 



No. 6, Cam. Inst. Wash., November 1903. 

 ' MacDougal, D. T., Botanical explorations in the Southeast. Journal of N. Y. Bot. Garden, vol. v, p. 89, 1904. 

 Note. — A copy of a paper by Mr. W. N. Sands giving " An account of the return of vegetation and the revival of 

 agriculture in the area devastated by the Soufriere of St. Vincent in 1902-3 " (West Indian Bull., vol. xii, pp. 22- 

 33, 1912) has been received since this paper was put into type. Some interesting facts as to revegetation of de- 

 nuded areas are given. 



