MOVEMENTS OF VEGETATION IN THE SALTON SINK. 147 



decayed. Baccharis appeared as a pioneer on the muddy Imperial Junction beaches in 

 1907 and 1908 and also on Obsidian Island, where it became strongly established. A 

 single individual was one of the first two plants on Cormorant Island in 1908, but only a 

 single individual was added to the place in the following four years. It also appeared on 

 the archipelago near Big Island as found in 1912. All of the introductions were in places 

 suggestive of wind deposition, and in the southeastern part of the lake. The locations are 

 those most liable to receive material by southeast winds from the Delta, in which the species 

 is especially abundant. The original introduction on Obsidian Island was still flourishing in 

 October 1912, and the single plant on Cormorant Island had survived until the same date. 



Oligomeris glaucescens is the sole representative of the Resedacese in this region. It 

 is a glaucous herb, branching at the base, with the branches ascending; its terminal flower 

 spikes become mature around the Salton in April and May, while the ripe capsules con- 

 taining seeds are found in place as late as the following February. The seeds are very 

 rounded and slimy and their weight and dimensions appeared to be about the same as 

 those of Sesuvium. Dried capsules from herbarium species collected in February 1908 

 were broken up and the mass of chaff and seeds was thrown into a vessel of Salton water 

 November 25, 1912. No exact account was made of the number of seeds, but about three- 

 fourths sank within a day. No further change was noted until the preparation was placed 

 in a sun-lighted glass house on January 20, 1913, when all of the remainder of the seeds 

 sank within a day. A single germination was noted 86 days after being wetted, and a 

 dozen more were noted March 10. Preparations were made for "stranding" the lot, but 

 all began to degenerate and were dead within a week. These reactions and the occurrences 

 of the species only in 1907 and 1908, on the shores at Imperial Junction Beach, Mecca, 

 and Obsidian Island, suggest that the condition barring the species from later emersions 

 consisted of the increased salinity of the water. The small size of the seed would make 

 it liable to be carried about by birds, while the period of flotation indicated would cause it 

 to be carried for distances between Obsidian Island and the shores to the southward. It is 

 notable that it did not appear on the steeply sloping beaches of Travertine Terraces. 



Isocoma veneta var. acradenia is a perennial composite especially abundant on the 

 slopes and bajadas west of the lake, and generally found on very arid locations. The pappus 

 bristles are stout and it does not appear liable to be carried long distances by the wind. 

 Fruits taken from an old dried specimen were put into a dish of Salton water on Novem- 

 ber 25, 1912, and a few sank every day, so that all were on the bottom a month later. The 

 proportion of perfect seeds is probably small and only two good embryos were found in the 

 entire lot on January 25, 1913, at which time no indications of activity had been shown. 



This plant was found on the emersions after they had been bare for some time, two 

 years generally, and then only on the western shore, in positions into which they might 

 have been carried by the wind or run-off streams from the parent plants which were only 

 a few hundred yards away. 



Juncus cooperi is a rush of limited distribution in the deserts of the Colorado and 

 Mohave, occurring around saline springs. The reddish-brown cylindrical seeds weigh 

 about 0.015 mg. and are furnished with an appendage which readily absorbs water. Despite 

 this fact the seeds floated from November 1G until December 4, at which time only 10 of 

 the original 100 sank, and the remainder followed on the 23d, showing a flotation period 

 of 37 days. Germination began soon after sinking, and by January 10, 1913, the hypo- 

 cotyls were seen emerging from nearly all of the seeds on the bottom of the vessel. The 

 seedlings became entangled by the extremely long trichomes which arise from the base 

 of the hypocotyl, and rose to the surface in clumps with illumination and warmer weather 

 late in January. Some of these clumps were "stranded" on January 29 and had taken 

 hold a week later. The schedule of the species is thus seen to include three weeks of flota- 

 tion of some of the seeds, which is extended to nearly twice that time in others. Germina- 



