166 



THE SALTON SEA. 



variation in the number of species introduced year by year is seen to be large, a fact which 

 suggests that the lack of a wind in a certain direction during the fortnight in which seeds 

 are falling from the parent plant might materially restrict their dispersal, while an oppor- 

 tune storm would carry light or appendaged seeds to a much greater distance. The number 

 of events which might influence any agency in moving seeds are almost countless. Thus 

 the feeding habits of the fish which are preyed upon by pelicans and cormorants might 

 result in variations in the part played by these birds. Rainstorms moistening the surface 

 layers might not only furnish favorable conditions for germination, but also carry a large 

 supply of seeds of various species down the slopes, etc. Mention has already been made 

 of the possible effects of rapid and slow evaporation by which stranded seeds would be 

 left behind on soil from which evaporation was very great. 



The analyses of the annual census shows that Atriplex linearis, Lepidium, and Cucur- 

 bita did not find a place on the beaches after the first recession in 1907, and that Atriplex 

 polycarpa and Phragmites dropped out of the pioneer class after 1908; Pluchea sericea, 

 while coming on many of the beaches later, did not figure as an innovator after 1909, and 

 Atriplex canescens and Typha stopped in 1910; Pluchea camphorata began appearing among 

 the pioneers on Travertine Terraces in 1910, although it was one of the first plants to be 

 seen on one of the sterilized islands. Six and probably seven species, therefore, which 

 originally came with the first occupants of the two special areas noted above, had dropped 

 out within the first four years of the recession of the lake. Such defection suggests at once 

 a restricting factor in the concentration of the water of the lake saturating the soils of the 

 beaches, together with the proportions of certain constituents. The only features which 

 might have a bearing on this matter are shown in table 34. 



Table 34.- — Concentration and proportion of certain constituents of Saltan water (per cent). 



The differentiation of the action of the elements in such a complex mixture as that 

 presented by Salton water is not easily made. While the increasing disproportion between 

 sodium and calcium might offer itself as a feature accounting for toxicity, yet it is to be 

 seen that even as late as 1912 the amount of the latter present would suffice to balance 

 the sodium. The great amount of chlorine suggests that it is to this substance that the 

 increasing toxicity might be ascribed. 1 



SUCCESSIONS AND ELIMINATIONS. 



The successions or transitions in the vegetation of arid shores of bodies of either salt 

 or fresh water are very abrupt, as has been found by the examination of great stretches of 

 the coast of the Gulf of California. The tidal zone may bear such plants as Laguncularia 

 and other tide-marsh plants, but immediately above the action of the waves the vegetation 

 of the desert finds place. 



The ephemeral character of Salton Lake with its rapidly sinking level called into action 

 a set of conditions entirely different from those to be met on the shores of a body of water 



1 Niklewski Bronislaw. Ueber den Austritt von Calcium- und Magnesiumionen aua der Pflanzenzelle. Ber. d. Deut. 

 Bot. Geeell., vol. xxvn, p. 224, 1909. 



