232 CLIMAX FORMATIONS OP NORTH AMERICA. 



Spirostachys, and Svaeda early in 1908. Late in 1908 Amaranthus, Baccharis, 

 Distichlis, Heliotropium, Oligomeris, Rumex, Sesumum, and Typha had dis- 

 appeared. Late in 1909 Atriplex canescens, A. fasdculata, Suaeda, Pluchea 

 sericea, Spirostachys, and CucurMta still survived, while a secondary introduc- 

 tion of Baccharis and of Chenopodium had taken place, both being represented 

 by only a few individuals, and these did not maintain themselves. 



"Atriplex canescens, A. fasdculata, and Spirostachys had multipUed and 

 thrived in 1910, while Suaeda seemed to have not multiplied; Pluchea was 

 losing a large share of its individuals as a result of the desiccation. The cen- 

 sus in 1911 was practically that of 1910 with the added losses of Pluchea, and 

 no change in the balance was visible late in 1912. The original sowing of 

 this place included 17 species, 8 of which had disappeared within a year; one 

 of the remaining 8 was lost in the following year, and two of the original pio- 

 neers were reintroduced only to disappear quickly. The census showed only 

 5 species in 1910, a!ll of which were still in evidence in 1912, but with Pluchea 

 sericea losing ground. The full return of the area to the conditions prevailing 

 up the slope might bring in Franseria or an occasional Larrea or Olneya, while 

 the number of individuals of the other species would be reduced on account 

 of the diminished soil-moisture supply. It is to be noted that the changes 

 here are wholly and directly connected with the water supply, and that the 

 survivors are halophytes, one of which was undergoing deterioration by reason 

 of the inadequate supply. 



"The original introductions on the emersions of 1907 of the Travertine 

 Terraces comprised two species, Atriplex canescens (from seeds which had 

 fallen down a caving bank) and Phragmites (which had washed ashore as a 

 rhizome) . The cut bank may have figured as a mechanical trap for grounding 

 wind-borne seeds, or some other condition may have come in, for now Atriplex 

 polycarpa, A. canescens (reintroduced), Bouteloua, Astragalus, Distichlis, 

 Heliotropium, Juncus, Pluchea camphorata, Prosopis pid)escens, Phragmites, 

 Sesuvium, Spirostachys, and Suaeda (13 in all) were present. The place was 

 not seen again until October 1910, when only Distichlis, Prosopis pubescens, 

 Phragmites, and Astragalus remained. 



"Late in 1911 Astragalus was not found, although as an annual its seeds 

 were probably present, while Pluchea sericea and Salix nigra had come in, 

 making 5 species with another probably present. Late in 1912 all of the above 

 elements had come'fn except Salix and Isocoma, while a single small plant of 

 Prosopis glandulosa was recognized, which had probably been confused with 

 P. pubescens, up to that time. The surface was fully occupied, and of the six 

 species present it seemed likely that Phragmites, Distichlis, and PliKhea would 

 soonest perish on account of the increasing aridity. The final condition of 

 this beach would probably be one in which Isocoma would endure, although 

 no estimate of the behavior of the other species can be made except to point 

 out that they are not on the slope just above the high level of the lake, which 

 is of the extreme desert type of this region. 



"The two beaches which have thus been analyzed display different types 

 of behavior. The gently sloping alkaline Imperial Jimction beach received 

 a sowing of 17 species during the first year of emersion and no secondary 

 introductions. The stress of increasing aridity has depleted the number of 

 the pioneers until but 5 species remain, of which one, Plv£hea, will soon fail 

 for lack of sufficient soil-moisture. The final flora of the slope will probably 

 consist of species now occupying it, but with greatly reduced number. An 

 occasional individual of one or two other species may come in. 



"The Travertine Terrace of 1907 was probably subject to wave action dur- 

 ing the greater part of that year and its original occupants may be taken to 



