130 THE SALTON SEA. 



serious changes may have come from the agricultural operations. The species named, 

 however, are represented abundantly in the area above the water-level and would be the 

 readiest invaders and occupants of any bare surface in their neighborhood. 



The expedition proceeded directly from this place to the beach at Travertine Terrace. 

 The strand originally laid bare in 1907 had been open to occupation for six years. Phrag- 

 mites, one of the first two pioneers, was still present. Prosopis pubescens was present in 

 a vigorous young tree, which was originally noted in 1908. Mats of Distichlis were abun- 

 dant, and Pluchea sericea was represented by a small number of individuals. Astragalus 

 was in the form of mature shoots with emptied seed pods, while a plant new to the area, 

 Isocoma veneta var. acradenia, was present, being the only innovation noted here for an 

 extended period. The soil and moisture conditions from a superficial examination appear 

 to be similar to those in which these plants ordinarily grow, with the exception of Phrag- 

 mites, and they may be expected to survive for an indefinite period. 



After some water travel for the inspection of islands, the results of which will be de- 

 scribed later, a landing was made on Obsidian Island on October 16, 1912. The seven 

 trees of Prosopis (2 species) previously noted were alive and growing rapidly. Heliotr opium, 

 Sesuvium, Baccharis, Spirostachys, Atriplex canescens, A. fasciculata, A. hymenelytra, and 

 Pdrosela emoryi were represented in the flora of the strand of 1907. 



It is probable that this last-named species had been overlooked on some visits, as it 

 appeared to have had a place since its original introduction. Cucurbita, however, had 

 dropped out, although, as will be shown later, it came on the beaches of succeeding years. 

 Sesuvium likewise was missed on some visits, though probably continuously present. The 

 conditions in this area are much different from those at the Travertine Terraces. In the 

 last-named locality the ancient beaches offer an example of the final fate of strands, and 

 those recently formed will doubtless progress by slow stages to the same condition (see 

 Plate 29 b). The continued flow of the Alamo and New Rivers into the southwestern part 

 of the lake, however, resulted in the deposition of a layer of silt which forms fresh soil 

 with low salt content on the beaches of Obsidian Island and Imperial Junction beach. 

 The return to alkaline desert conditions here would be far slower, and hundreds of years 

 might be necessary for the physical changes which would ultimately bring the lower slopes 

 to the same state as the upper slopes untouched by the last inundation. 



A resume 1 of the history of the strand of 1907 during its first six years of desiccation 

 will lead to a more intelligent consideration of the strands of lower level which will be taken 

 up in the succeeding sections. 



The pioneers on the gently sloping Imperial Junction beach were Atriplex canescens, 

 A. linearis, A. polycarpa, A. fasciculata, Suceda torreyana, Spirostachys occidentalis, Pluchea 

 sericea, and Distichlis spicata on the plane slopes, while the filled channels of the washes 

 with a larger moisture content and lower proportion of salts gave lodgment to Heliotropium 

 curassavicum, Typha angustifolia, Rumex berlandieri, Leptochloa imbricata, and Lepidium 

 lasiocarpum. Several hard-shelled fruits of Cucurbita palmata had been cast ashore, but 

 no activity had been shown by the seeds. To this census, made in February 1908, may be 

 added Oligomeris glaucescens and Baccharis glutinosa, on the plane slopes, while Amaranthus 

 palmeri and Sesuvium sessile were added to the population of the filled washes. 



It may be said at once that no secondary invasions occurred on the plane slopes and 

 that no new species were added to the population of this emersion, although Baccharis, 

 Typha, and Amaranthus appeared in new individuals, which apparently were brought in 

 independently, not originating from those already present. All of the invaders had 

 perished in October 1911, except Suceda, Atriplex, and Spirostachys, while some Pluchea still 

 survived in scattered spots. 



The slope at Mecca was even gentler than the one just described and the succession of 

 events may not be so succinctly related. The occupants of the strand of 1907, as examined 



