MOVEMENTS OF VEGETATION TN THE SALTON SINK. 165 



and deposited on the margins or in bars, and the seeds which survive the attrition they 

 receive during such movement would, some of them, come to rest in layers of moist sand, 

 in which germination might speedily ensue. Species with a long resting period might lie 

 dormant until a favorable condition of moisture or temperature were encountered. Among 

 the species observed which may be definitely assigned to the class moved by run-off are 

 Astragalus, Bouteloua, Chamcesyce, Coldenia, Conyza, Encelia frutescens, Hilaria, Hymenochloa, 

 Oenothera, Olneya, Parosela emoryi, and Wislizenia. The distances traversed were not in 

 any instance over a mile or two and it is evident that, when the movement of a plant this 

 distance down a gentle slope is considered, many forces (including winds and animals) might 

 play a part, although perhaps a minor one. Obviously the action of the run-off streams 

 would contribute to give the recession of the first year from the maximum level of the 

 lake a flora far richer in number of forms than that of any succeeding year. 



SPECIES APPEARING EARLIEST ON THE BEACHES. 



A profitable comparison of the initial species on newly emersed beaches may be made 

 by a review of the observations of the plants on Imperial Junction Beach with a slope of 

 1 to 300 and an alkaline adobe soil, and on the Travertine Terraces with a slope of about 

 1 in 20, upon which the water cut terraces and shelves. 



Amaranthus, Atriplex canescens, A. fasciculata, A. linearis, A. polycarpa, Cucurbita, 

 Baccharis, Heliotropium, Lepidium, Leptochloa, Oligomeris, Pluchea sericea, Rumex, Sesu- 

 vium, Spirostachys, Suada, and Typha appeared on the emersion of 1907 at Imperial Junc- 

 tion Beach, as noted in the early part of 1908, while only Atriplex canescens and Phragmites 

 were included in the first plants on the beach of 1907 at Travertine Terraces. 



Atriplex fasciculata, A. polycarpa, Leptochloa, Scirpus paludosus, Spirostachys, Typha, 

 Suwda, and Polypogon were found on the emersion of 1908 at Imperial Junction Beach and 

 Typha, Heliotropium, Distichlis, Pluchea sericea, Phragmites, Bouteloua, Salix, and Populus 

 on the beach of the same year at Travertine Terraces. 



Leptochloa, Scirpus, Typha, Heliotropium, Pluchea sericea, Sesuvium, Suceda, Spiro- 

 stachys, Atriplex fasciculata, and A. canescens came on the emersion of 1909 at Imperial 

 Junction Beach. Distichlis, Heliotropium, and Pluchea camphorata comprised the entire 

 census of the Travertine emersion of 1909 when visited in 1910. 



Heliotropium, Leptochloa, Scirpus, Atriplex fasciculata, Spirostachys, and Suaida were 

 the first species to come on the emersion of 1910 at Imperial Junction Beach; Distichlis, 

 Heliotropium, Populus, and Salix made up the entire pioneer flora of the beach of 1910 at 

 Travertine Terraces. 



Scirpus, Leptochloa, Heliotropium, Distichlis, Sesuvium, Rumex, Sweda, and Spiro- 

 stachys came first on the emersion of 1911 at Imperial Junction Beach, while the emersion 

 of 1911 at Travertine Terraces (when the census was taken as in previous years, late in 

 the autumn) showed only Distichlis, Salix, and Populus. 



Atriplex fasciculata, A. lentiformis, Suceda, Spirostachys, Scirpus, Sesuvium, Distichlis, 

 and Leptochloa came into the emersion of 1912 during that year at Imperial Junction 

 Beach, while Sesuvium, Salix, Populus, Atriplex lentiformis, Spirostachys, Heliotropium, 

 Prosopis pubescens, and Pluchea camphorata appeared on the shelf of 1912 at Travertine 

 Terraces. 



Numerically as to species, the pioneer flora of the alkaline beaches in the series of 

 six years ran 15, 8, 10, 6, 8, and 8, while that of the steeper sandy and gravelly benches 

 of the Travertine Terraces formed a series of 2, 8, 4, 3, and 8. The average number of 

 species appearing on Imperial Junction Beach was nearly twice as great as that on the 

 Travertine Terraces, the low gradient of the slope of the beach being favorable to the 

 introduction and establishment of plants, while the alkaline soil appeared to afford con- 

 ditions for halophytic forms superior to those of the Travertine Terraces. The range of 



