MOVEMENTS OF VEGETATION IN THE SALTON SINK. 137 



REOCCUPATION OF THE STRANDS OF 1911. 



The total recession during this year was about 49.6 inches. The soluble salt-content 

 of the water amounted to about 0.7 per cent at the beginning of the year. 



A visit was made to the Imperial Junction beach in April 1911 by Mr. E. E. Free, 

 who reported a band of vegetation, about 200 feet in width, extending up the slope from 

 within 50 feet of the margin of the water. In following this for half a mile, Scirpus palu- 

 dosus, Leptochloa imbricata, Heliotropium, Distichlis spicata, Sesuvium, Rumex, Spirostachys, 

 and Suceda were seen. An examination of the zone in September of the same year brought 

 to light only Spirostachys, Suceda, and Distichlis. It was notable that Atriplex had ceased 

 to be a pioneer on this beach. (See Plate 24 b.) 



The strand of 1911 at Mecca bore Typha, Scirpus, Atriplex lentiformis, and Spiro- 

 stachys when examined in June 1912. Most of these appeared to be surviving when the 

 place was visited in the following October. 



The strand of 1911 at Travertine Terraces bore only Distichlis, Salix, and Populus 

 in September of that year, which was also a notable departure from the history of previous 

 strands. In June 1912 Distichlis, Heliotropium, and Spirostachys were seen on the shelf, 

 while the remaining vegetation consisted of Salix, Populus, Typha, Pluchea sericea, P. 

 camphorata, and Scirpus paludosus, largely collected in a dense rank at the upper margin. 

 In October the rank at the upper margin of the strand included Salix, Populus, Prosopis 

 pubescens, Typha, and Pluchea sericea, while Pluchea camphorata, Scirpus olneyi, Spiro- 

 stachys, Sesuvium sessile, Heliotropium, and Distichlis were now found on the floor of the 

 terrace. (See Plate 24 a.) 



The recently bared strand of Obsidian Island was vacant. 



REOCCUPATION OF THE STRANDS OF 1912. 



The water of Salton Lake had increased in concentration to such an extent that it 

 contained nearly 0.9 per cent of dissolved material by June 1, 1912. The deposition of 

 calcium as a carbonate had continued at such rate that emersed objects, such as twigs 

 and branches of trees, were heavily coated with lime. The toxic action of the water would 

 probably be greatly increased by this disturbance of the balance. 



The strand of 1912 at Mecca was well dried out in places and offered much efflorescence 

 when examined in October. Scattered over it and collected in favorable spots were Atriplex 

 lentiformis, Pluchea sericea, P. camphorata, Spirostachys, Populus, Heliotropium, Typha, 

 Salix, Distichlis, and Scirpus paludosus, an invasion which for numbers was foreshadowed 

 by the plants seen on the emersion of 1911. 



No plants were found on the ground laid bare by the recession of 1912 at Travertine 

 Terraces in this year, in June, except Sesuvium. In October, however, the angle at the foot 

 of the distinctly cut bank, which may be taken to mark the upper margin of this strand, 

 included Salix 2 or 3 feet in height, Populus, Atriplex lentiformis, Spirostachys, Heliotropium, 

 Prosopis, and Pluchea camphorata represented by active young plantlets, while Sesuvium 

 was found both at the top and foot of the low bank. (Plate 25 b.) 



A visit on the following day showed that the strand of 1912 on Obsidian Island was 

 still bare. Two days later the inspection of the Imperial Junction beach was made. The 

 uppermost portion bared early in the year bore a dense zone of Atriplex lentiformis, A. 

 fasciculata, Suceda, Spirostachys, Scirpus paludosus, and Sesuvium. A second zone near 

 the margin of the water, representing germinations of the midsummer, included Distichlis, 

 Leptochloa, Scirpus paludosus, and Atriplex lentiformis. 



It is to be seen from the above that the successful invasions of 1912 number far more 

 than those of the preceding two or three years on most of the beaches. So far as the Im- 

 perial Beach is concerned more favorable conditions may well be ascribed to the silt thrown 



