56 REPORTS OF INVESTIGATIONS AND PROJECTS. 



MOVEMENTS OF VEGETATION AROUND THE SALTON SEA. 



The phenomena presented by the reoccupation of the emersed areas around 

 the Salton Sea by plants have been of a pronounced character and the reac- 

 tions observed have been capable of easy interpretation. From the maxi- 

 mum, which was reached on February 10, 1907, to February 10, 1908, the 

 level of the water fell 40 to 42 inches. This recession laid bare beaches a few 

 feet in width on the steeper slopes and over 400 yards in others, and was 

 accompanied by an increase of the salt content from t,t,t, parts in 100,000 in 

 February, 1907, to 364 parts in June, 1907, and 460 parts in June, 1908. The 

 analyses also show that the amount of organic matter in the water is less than 

 at the time of maximum depth of the water. Some algae clinging to the rocks 

 along the shore include all of the aquatic vegetation at the present time, while 

 the fauna appears to be limited. 



The wave action on the steeper gravelly shores is operating to produce 

 terraces, dunes, and tide pools, with an accompanying sorting action of the 

 material moved. The results of similar action on old beaches higher up are 

 still denoted by differentiated bands of vegetation after many hundreds or 

 perhaps thousands of years. 



Results of somewhat wider importance, however, are being obtained on 

 gentler slopes, such as those presented by observational area No. i, in which 

 the soil before immersion was highly impregnated with alkaline salts. The 

 water of the lake being less salty, dissolved out much of the alkali, so that as it 

 receded the plants from the shore found this area too little salty and are occu- 

 pying portions of it with difficulty. Capillary action, however, is bringing ad- 

 ditional quantities of alkali to the surface, so that these plants will gradually 

 spread over and reoccupy the zone. On the other hand, myriads of seeds of 

 species inhabiting areas in which the soil contains but little salt are stranded 

 by the receding water and germinate in the moister soil. As it gradually be- 

 comes drier, and the alkali in the surface layers increases, the individuals aris- 

 ing from the water-sown seeds come into an increasing degree of stress with 

 these factors. Thus many thousands of arrow-weed (Pluchca sericea) and 

 cat-tail (Typha angustifolia), as well as other species in lesser numbers, are 

 annually sown in the most recently emersed zone, and as this becomes drier 

 and saltier a selective action is exerted which reduces the number alive in such 

 an area until a year later it is but a small fraction of the original. Each sea- 

 son adds another band to the series, and it remains to be seen whether or not 

 this selective action will result in the survival of any individuals much beyond 

 that of the mass, and the final fate of their progeny. 



At the present stage of the investigation the efficiency of water as an agency 

 in the dissemination of plants is emphatically demonstrated. Wind as a direct 

 and independent factor has been operative to but little extent in the revegeta- 



