MOVEMENTS OF VEGETATION IN THE SALTON SINK. 135 



The dissolved salts in the water had reached a proportion of over 0.5 per cent, or 520 

 parts in 100,000, in June of this year, and some lowering of the rate of increase in the calcium 

 was also noticeable. The conjoint effect, however, of all of the conditions enumerated was 

 a greater number of successful invasions of the emersed strip. 



The occupation of the newly bared beach at Imperial Junction was characterized by 

 a zone of plants of indefinite width coming to within 300 feet of the margin of the water 

 late in October 1909. This position was one indicative of midsummer germinations in 

 mud moistened by the summer rainfall. Leptochloa imbricata, Scirpus paludosus, Typha 

 angustifolia, Heliotropium curassavicum, Pluchea sericea, Sesuvium sessile, Suceda torrey- 

 anum, and Spirostachys occidentalis were present, the last two being the most abundant and 

 evidently coming from seeds, while the single plant of Typha was growing from a rhizome 

 washed ashore. The two species of Atriplex on this shore were present in the midwinter 

 zone with Suceda and Spirostachys. The collection of precipitation water had furnished 

 a supply of moisture for the plants growing in the filled channels of the washes above the 

 1909 zone. 



A visit a few days later to the beaches of Obsidian Island resulted in the detection of 

 vegetation on the emersion of 1909, which was the only time in which plants were seen to 

 appear here during the first year of the emersion. The sowings were composed of Helio- 

 tropium, Amaranthus palmeri, Sesuvium, Spirostachys, and two species of Atriplex. The other 

 observational areas were not inspected during this year. 



In May 1910 the strand of 1909 on Imperial Junction beach included Heliotropium, 

 Suceda, Atriplex (2 species), Spirostachys, Sesuvium, and Cucurbita, the last-named being an 

 innovation, while Leptochloa, Scirpus, Typha, and Pluchea sericea had perished. (Plate 28 a.) 



The strand of 1909 at Travertine Terraces bore only Distichlis, Heliotropium, and 

 Pluchea camphorata in September 1910. A year later the entire emersed zone at this place 

 was heavily carpeted with Distichlis, which was also noted in abundance on the soil laid 

 bare during 1909; scattering clumps of J uncus, Salix nigra, Prosopis pubescens, and Astraga- 

 lus were also found. The entire population was thus seen to be different from that of 

 Imperial Junction beach. 



The 1909 strand on Obsidian Island showed only Spirostachys and two species of 

 Atriplex in October 1911. 



The heavy carpet of Distichlis persisted at the Travertine Terraces and was examined 

 in June and October 1912. Cyperus, Astragalus, Pluchea camphorata, P. sericea, Prosopis 

 pubescens, and a single Salix were seen in June. Cyperus was not found in October 1912, 

 but Isocoma and Heliotropium had come in. A supplementary visit was made in February 

 1913, at which time Atriplex lentiformis, A. canescens, and Juncus cooperi were added to 

 the above list. (Plate 22 a.) 



The limits of the emersion of 1909 at Mecca were not to be accurately determined, 

 but a photograph was made of a large Atriplex lentiformis and some Spirostachys, both of 

 which were under very favorable conditions, in October 1912. 



The only plants which could be identified at this time as positively on the emersed 

 strip of 1909 on Obsidian Island were Parosela emoryi, Cucurbita palmata, and Spirostachys; 

 Atriplex of two species and perhaps also Heliotropium might be safely included. 



In 1912 only Spirostachys and Suceda appeared to be surviving of the large number of 

 invaders which had found a foothold on the moist strand at Imperial Junction beach in 

 1909. The first of these was making a maximum shoot development. 



An analysis of the movements of plants on the strands laid bare in 1909 similar to 

 that made for the two years previous brings out the following: The invaders of the bared 

 strip at Imperial Junction beach included 10 species at first, which was reduced to 7 in 

 May 1910, by four fatalities and one additional intruder, while the close of the observa- 

 tions was made with only the two halophytes, Spirostachys and Suceda, persisting. 



