122 THE SALTON SEA. 



halophytic vegetation, inclusive of Spirostachys, Suceda, Atriplex, and Franseria, while 

 Olneya and Larrea were represented by a few individuals back some distance from the 

 shore. A few drainage channels or dry washes cut to a depth of a yard or less ran directly 

 down the slope and offered special conditions when submerged. 



The water rose rapidly to the maximum level, and the extreme upper strip covered 

 was submerged for a few days, less than a week, even when wave action is taken into 

 account, and then the recession began as illustrated by the curve in figure 3. The bared 

 zone had a width of about 1,000 feet in February 1908, and the average rate of horizontal 

 recession was therefore about a yard daily. Much less than this would be laid bare during 

 the winter months, while during the season of maximum evaporation in the summer as 

 much as 1.5 yards must have been uncovered daily. 



The first critical examination of the Imperial Junction area was made in February 

 1908, or almost exactly a year after the recession began. The extreme high-water level 

 was marked by a ragged band of timbers, drifted wood, and rounded masses of pumice 

 for many miles along this shore, which was exposed to almost direct action of storms coming 

 from the northwestward through the San Gorgonio Pass. The abruptly walled channels 

 of the shallow washes which had been submerged were filled with mud by the action of 

 the waves, and when these deposits were uncovered offered slightly different soil condi- 

 tions from the contiguous slopes upon which there had been very little sorting of material 

 (see Plate 12c). No strand or beach ridges were visible and perhaps the only actual changes 

 were those in the washes just noted and also in the salt and moisture content. The water 

 of the lake when at the high level did not contain over 0.3 per cent of dissolved salts, but 

 by January or February 1908 it had increased to about 0.4 per cent, although no estimation 

 was made until June, at which time the total dissolved salts amounted to 0.46 per cent. 

 This amount was probably much less than that present in the soil of the observational 

 area, in consequence of which a leaching action must have ensued which resulted in fresh- 

 ening the soil to some slight depth. (See Free, pp. 30-33.) 



The uppermost portion of the strand, or that part of it which must have been flooded 

 by the advancing water in December 1906 and January 1907, and laid bare before May 



1907, was occupied by a dense formation of Suceda torreyana, Amaranthus palmer i, Atriplex 

 fasciculata, A. canescens, A. linearis, and Spirostachys occidentalis. The last-named extended 

 below the limits of the others to a point probably representing the stage of the water in 

 June 1907. Immediately below the Spirostachys was a dense band of Pluchea sericea, the 

 individuals of which were from a few inches to a yard in height. 



Seeds of Suazda, Atriplex, and Spirostachys probably were present in the surface layers 

 of the soil at the time of the inundation, and as the zonation was repeated on the corre- 

 sponding seasonal recession of succeeding years the influence of germination conditions 

 is suggested as the determining factor in all of them. The compositaceous Pluchea did 

 not inhabit this area originally; its crops of seeds are ripened in early summer and are 

 blown about by the wind in enormous numbers. The probabilities are great that some seeds 

 were carried to lodgments on the muddy shore directly by air-currents. Some may have 

 fallen in the water and were then cast ashore by wave-action. Any remaining afloat would 

 be subject to the toxic action of the water, toward which the various species showed specific 

 endurance (see Plate 16 a). 



A wide zone of hard bare dry soil below the zone of Pluchea was found in February 



1908, which was taken to be the strip laid bare in midsummer, during which time the 

 horizontal recession would be 4 or 5 feet daily. This action, coupled with the high summer 

 temperatures, would result in such rapid desiccation of the surface of the soil that deposited 

 seeds would not be under suitable conditions for germination very many days. The actual 

 rate of evaporation and concomitantly that of recession is suggested by the figures given 

 in tables 32 and 33, page 134, which have been plotted from the data given in the section 



