156 THE SALTON SEA. 



side of the lake, but it disappeared within a year after this date. It is to be noted that the 

 species was found on the higher parts of islands not reached by the flood and that it inhabits 

 localities of extreme aridity. 



Franseria dumosa appeared in the emersion of 1907 on the western shores of the lake, 

 to which place it was probably carried by run-off streams. The soil conditions would 

 favor its survival. This plant is a constituent of the final formation on old beaches. 



Heliolropium curassavicum was one of the earliest pioneers on almost all of the beaches, 

 being found in bloom on the 1907 emersion as early as February 1908. It is notable, how- 

 ever, that with the progressive desiccation of the beaches it perished within two years, 

 except in such places as the Mecca area, where the low, gently sloping beach had a high 

 soil-moisture content, and on Obsidian Island, where the beaches were so steep that the 

 actual distance from the margin of the water of the receding lake and the original strand 

 was comparatively small. 



It was consistently included among the pioneers in the successive emersions studied, 

 and likewise appeared to be injured very quickly by any notable decrease of soil-moisture. 

 Heliolropium came in on the islands of the archipelago south of Big Island in 1908, but 

 Cormorant Island, the most isolated of all of the emersed areas, did not receive it until 

 1912, when two plants in bloom were found on its upper slopes. The transportation to 

 this place may be attributed to birds, with a high degree of probability, especially as the 

 seeds are very small and sink within a short time. No opportunity was afforded for testing 

 the flotation of the seedlings. The two plants found were on a spot that must have been 

 above the water for at least two years and they had germinated and come to bloom within 

 the year, after the manner of freshly deposited seeds. 



Hilaria rigida was noted but once, and then on the zone laid bare by the recession of 

 1907 on the western side of the lake. The species is native of the higher slopes to the west- 

 ward and the seeds might have been carried down the slopes by run-off streams. Nothing 

 is known as to the survival of early introductions, but the species might be expected ulti- 

 mately on such slopes. 



Lepidium lasiocarpum appeared in the silt-filled channels of the washes on Imperial 

 Junction beach following the recession of 1907, but apparently did not survive long or 

 withstand the progressive desiccation, the effects of which were very marked in this locality. 



Lippia nudiflora came onto the beach of Obsidian Island at the same time as Psatlirotes 

 and Sphwralcea and formed distinct mats on the southeastern shore, which persisted during 

 all of 1908, but had perished when the place was visited in October 1909. The weight of 

 inference would suggest flotation to the place, either in the form of seeds or living stems. 



Oenothera scapoidea aurantiaca came down onto the strand of 1907 with Franseria 

 and Wislizenia and also appeared on Obsidian Island, to which place it may have been 

 carried either by waves or by birds. It is surmised that its seeds would not endure long 

 immersion in salty water. It disappeared from the ranks of invaders on the shore of the 

 island within a year, but probably follows down the gravelly slopes on the western side 

 of the lake by irregular seeding and establishment. 



Olneya tesota occurs with some frequency up the slopes of the Sink in all directions 

 from the lake, but its seedlings were seen but once on the emersed zones. This was in the 

 emersion of 1907 and the observation was made in November 1908. It seems probable 

 that the beans were washed down the slopes by run-off streams. 



Parosela emoryi was in many respects one of the most important species which appeared 

 on the beaches. It came on the emersion of 1907 on Obsidian Island, which it must have 

 reached by flotation, and was seen there in 1908. A second invasion in the same year was 

 noted on the southwestern side of the lake. The original location on Obsidian Island was 

 still held in October 1912. Occurrences in the emersion of 190S were also noted on the 

 southwestern side of the lake and on Obsidian Island below the introduction of 1907. A 



