148 THE SALTON SEA. 



tion begins about six weeks after contact with the water and seedlings which had floated 

 three weeks were capable of taking root when stranded. All of these periods would probably 

 be shortened in seeds liberated in late summer during warmer weather. 



The observations of this plant show that it came on the beach only at the Travertine 

 Terraces, where it appeared on the bared zones during the first year of emersion. Its ap- 

 pearance soon after the emersion of an old accretion mound of a saline spring in 1909 

 suggests that the stem-bases and perhaps the roots are capable of prolonged submergence. 

 The restricted establishment of the plant, with its comparatively long flotation period 

 of seeds and plantlets, is probably a matter of soil; both seeds and plantlets must have 

 been carried to many shores both by water and by birds. 



Leptochloa imbricata is an annual grass which appears to be abundant throughout the 

 Delta of the Colorado, where fruits consisting of the minute grains inclosed in the glumes 

 were collected by Mr. S. B. Parish in October 1912; 100 of these were placed in Salton 

 water on November 16, 1912, with the result that one germinated within 10 days, while 

 the remainder were still afloat and inactive until the end of January, when all of the sound 

 embryos awoke with the rising temperatures and increased illumination. After allowing 

 the plantlets to float for two weeks, the entire lot were "stranded," with the result that a 

 fair proportion took hold and sent roots down into the moist saline soil. 



The sole observations of this plant concerned its appearance on the emersed zones of 

 Imperial Junction beach and on Obsidian Island in 1907, 1908, 1909, 1910, and 1911. 

 Both places are directly affected by the inflowing current of the Alamo River from the 

 Delta, and in both the recession of the water is followed by a desiccation of the soil which 

 soon terminates the existence of the plant. It is notable that Leptochloa was not seen 

 in any position in which it might not have been deposited by waves and that the radius 

 of its dispersal does not extend more than 8 or 9 miles from the mouth of the fresh-water 

 stream which might bring it into the lake. The small fruits might readily adhere to the 

 feet of birds or to floating driftwood. 



Pluchea camphorata is a stoutish annual with its clumps of stems reaching a height 

 of about 2 feet in late summer. The achenes are furnished with capillary bristles and 

 these would be cast loose from the plant in time for germination in the warm weather of 

 autumn. Seeds collected near Mecca in mid-October 1912 were placed on the water on 

 February 11, 1913, and remained on the surface. The first germination was noted on 

 March 1 and during the next 10 days it appeared that practically the proportion that might 

 be expected had awakened. The fruits had not been separated, as a result of which small 

 tangled clumps of bristles and seedlings floated on the surface or were suspended at various 

 depths in the water. A test was now arranged by which the water in which the plantlets 

 were floating was poured into a glass dish filled half-full with packed soil. After this had 

 been done the dish was tilted at such an angle as to give a miniature beach and a half 

 dozen were "stranded" in the process. 



Representatives of this species were found on the emersion of 1907 in May 1908 at 

 Mecca, and it was seen to be distributed down the slope, following the recession of the 

 lake at similar intervals as late as 1913; but seeding did not always follow the first occu- 

 pation, and the plant was noted on the 1907 strand at Travertine Terraces, from which 

 it afterward disappeared, but it was noted here, on the emersions of 1909, on which it 

 persisted until the preparation of this manuscript, and it came in on the emersion of 1910 

 at the same place (Travertine Terraces). The emersion of 1911 was also occupied by this 

 plant at Travertine Terraces, and it was found on the islands which rose from the water 

 near Big Island in 1909. It is plain, therefore, that fruits or plantlets of the species are 

 transported across stretches of open water. The instances in which the occurrence of the 

 plant could be best correlated with the phenomena of emersion were at the Travertine 

 Terraces, and here the plant was not seen within a year's recession of the margin of the 



