MOVEMENTS OF VEGETATION IN THE S ALTON SINK. 155 



The introduction of this species by flotation and its subsequent survival on the beach 

 is in contrast with the conclusions reached by Guppy with regard to the transport of gourds 

 by ocean currents. Gourds are known to be carried by such means to points widely distant 

 from their place of origin, but Guppy maintains that establishment takes place only by 

 the aid of man. 1 The constantly receding water in the Salton offers conditions different 

 from those of sea-shores, and the gourd carried by its waters is a desert species which 

 encounters accustomed conditions when stranded on a desiccating gravelly or sandy beach. 



Cyperus speciosas is a sedge, the significant occurrence of which in this region is along 

 high-water channels of the Colorado River. It was found in the Delta lands by Mr. 

 Parish; also on the emersion of 1908 of Obsidian Island, which is directly in the way of 

 inflowing currents of the Alamo, which is in effect an effluent of the Colorado. It also 

 grew upon the 1908 emersion at Travertine Terraces as well as those of 1909 and 1910. 

 It may be probable that the later appearances are from seeds of the first introduction. 

 No tests were made of the flotation of the fruits, but it is probable that their small size 

 would render them liable to become attached to the feet of birds. 



Distichlis spicata was one of the most abundant of the pioneers and it appeared on 

 all of the beaches, although it soon perished under the stress of desiccation, especially in 

 such places as the slopes at Imperial Junction beach. The dispersal by seeds is probably 

 one of the most important means of dissemination, and in this both birds and waves might 

 play a part. Its appearance on a strand area was generally early in the year succeeding 

 emersion, but in some instances it followed the water closely, as it did one year at Imperial 

 Junction beach. The session of 1909 was characterized by heavy mid-summer precipita- 

 tion, but this resulted in no increase in the number of pioneers of this species during that 

 year. Beginning with 1910, however, it was seen that the beaches of 1909 everywhere 

 about the lake bore a heavier mat of Distichlis than the ground laid bare in any other year. 

 The disparity was evident as late as October 1912. 



The vigorous growth of the rhizomes is such that the plant soon spreads from its 

 original location to such an extent as to cross the boundaries of emersion zones. No ex- 

 perimental proof can be adduced, but the conditions suggest that detached rhizomes 

 might readily be carried long distances by the water of the lake. It is possible that the 

 immediate appearance of the species following hard on the recession may be due to the 

 "stranding" of such living stems. 



Eclipta alba was represented by one individual in the emersion of 1907 on Obsidi;m 

 Island, when examined in November 1908, and a year later the species was represented 

 in the emersions of 1908 in the same locality. Further observations of it in this place are 

 lacking and it probably did not reproduce itself on the invaded area. A third occurrence 

 was noted in 1909, on a newly emersed area near Big Island, which likewise had no result. 

 The fruits of Eclipta are known to be capable of flotation for many months, and the manner 

 of occurrence on the islands of the Salton suggests that the plant was carried to the beaches 

 in this manner. 



Encelia eriocephala made an appearance on the Travertine Terraces following the 

 recession of 1908, where it failed to survive, and a single fruiting individual was found 

 at the same time on the eastern shore of Obsidian Island. It failed to reproduce itself and, 

 although fruiting specimens were seen up the slope from Imperial Junction beach, it found 

 no further place on the bared areas. 



Eriogonum thomasii was first seen at flood level and slightly above it on Obsidian 

 Island in February 1908, as if the seeds had been carried to their places by birds or had 

 been moved short distances by them after being washed ashore by the waves. These 

 plants were seen three months later, and again in November 1908 on the southwestern 



1 Guppy, H. B., Observations of a naturalist in the Pacific, vol. n, pp. 570, 571, 1906. 



