140 THE SALTON SEA. 



" On the evening of June 20, 1912, the relative humidity at a distance of 3 or 4 miles from the 

 shore was 32, which showed no increase at sunrise on the following morning. It had already been 

 previously noted that contiguity to the Delta or bodies of water in an arid region does not necessarily 

 result in increased humidity, as evidenced by the fact that the amount of moisture in the air a few 

 yards from the banks of the Colorado River was but little different from that of the drier parts 

 of the desert widely separated from the Delta." • 



ENDURANCE AND SURVIVAL OF SEEDS AND PLANTS IN PLACE. 



The principal mechanical and chemical features of the Salton Sink now having been 

 fairly presented, it will be pertinent to turn attention to the mechanical relations and life 

 histories of the species which compose the aggressive hosts of plants which press upon 

 the bared areas as invaders and possible occupants of the empty areas. 



So far as the islands in Salton Lake are concerned, it may be assumed with fair cer- 

 tainty that their submersion in the saline water of the lake for a few weeks or a few months 

 would result in the destruction of all of the living plants except such forms as Phragmites, 

 Distichlh, Juncus, and Typha, species about which there is but little to discuss in the present 

 connection, since they are not nimibered among the pioneers on islands. Populus estab- 

 lished in boggy locations near flowing wells endured submergence of its roots to the depth 

 of a foot or two for a few weeks without material injury. 



The mounds of organic material surrounding saline springs 2 miles to the westward 

 of the railroad station of Salton, which had been submerged by the waters of the lake a 

 depth of a yard or more during the years 1907 and 1908, were found to show living rhizomes 

 and stems of Phragmites, Typha, Juncus cooperi, and Distichlis spicata. The water which 

 had covered them showed a total salt content of about 0.3 per cent at the beginning of 

 this period, which had increased to 0.6 per cent a year later. The species noted generally 

 grow in soils more or less highly charged with salts and their survival was in no wise un- 

 expected. The changes resulting in dead stems of shrubs and trees have received extensive 

 and detailed treatment by Professor Brannon in another section of this volume. 



The tops of many of the larger plants, such as Atriplex, Suceda, and Spirostachys, 

 with maturing seeds, the bases of the stems of which were surrounded by the waters of the 

 lake, were held aloft in place and a portion of the crop was not dropped until after the 

 ground around them was laid bare, with the result that a sowing was made without the aid 

 of other distributional agencies in freshly bared strands. This effect was most marked at 

 the extreme northwestern corner of the lake in 1908, and also to some extent on the north- 

 eastern shore, where the water covered a gentle alkaline slope. 



On gently rising slopes, like those near the northwestern end of the lake near Mecca 

 and on the eastern shore near Imperial Junction, the water flowed about the bases of the 

 shrubby vegetation, giving the spectacle of xerophytic forms growing under aquatic con- 

 ditions. Efflorescences and other deposits and accumulations of salts on the surface were 

 dissolved at once, so that samples of water like that taken near Travertine Point in May 

 1906 showed a total solid content 1,152.8 parts in 100,000, or over 1 per cent, of which 884 

 parts were common salt. This is about three times as much as in the main body of the 

 lake. This fringe of highly saline water would exert a stronger toxic action on seeds lifted 

 from the soil than the water of the body of the lake. The shallow layers of water near shore 

 attained a much higher temperature in the midday with the thermometer over 100° F. 

 than that farther out in the lake. Both the higher concentration and the higher tempera- 

 ture would increase the sterilizing effects of the rising lake. (See p. 121.) 



After both of these conditions have been allowed for, however, the supposition remains 

 that the submergence of the arid soil of the isolated islands might not destroy all of the 

 seeds present. The analysis of the manner in which a plant begins existence on a newly 

 emersed island should take this fact into account, although the consideration is largely a 



» MacDougal. The Delta of the Rio Colorado. Bull. Amer. Geog. Soc, vol. xxxvm, p. 4, 1906. 



