MOVEMENTS OF VEGETATION IN THE SALTON SINK. 163 



camphorata, P. sericea, Populus sp., Salix nigra, Sonchus asper, S. oleraceus, and Typha 

 angustifolia, a total of 12 species, or about 20 per cent of the total number. Three-fourths 

 of this number were carried to the sterilized islands, but not Populus, Salix, and Isocoma, 

 or rather it should be said that successful germinations of these were not seen. The beaches 

 on the islands offered conditions not at all suitable for any of these species and they were 

 lacking from the Imperial Junction beach perhaps for similar reasons. 



Positive evidence of the action of birds in carrying seeds is extremely difficult to 

 secure. The seeds of a large number of the species coming onto the beaches are very small, 

 and nearly all of those tested for flotation and germination would adhere to a rod of wood 

 or glass or to the finger when thrust into the water in which they were floating and then 

 withdrawn. Such adhesions would be greatly facilitated by even the smallest particle or 

 layer of mud and it seems reasonable to assume that many thousands of seeds must have 

 been carried about in this manner. Cryptanthe barbigera occurred on Obsidian Island in 

 such manner in 1908 as to suggest that the burr-like fruits may have been carried to the 

 shore by birds, while Spirostachys was found near nests of pelicans and cormorants in posi- 

 tions in which seeds may have been detached from the legs or feathers of a bird. In addition 

 to the species the seeds of which appear to be borne about by the wind only, Astragalus, 

 Chamcesyce, Coldenia, Eleocharis, Encelia, Franseria, Hilaria, Hymenochloa, Oenothera, Olneya, 

 Parosela emoryi, Prosopis glandulosa, and P. pubescens would not be liable to be carried 

 by the birds. The 34 remaining species offer many probabilities of introduction by birds, 

 although profitable surmise may not be made as to the actual importance of the plants 

 carried about in this way. (Plates 31 b and 32 b.) 



Attention is to be called again to the fact that the zonal arrangement of the initial 

 individuals on a beach would not be incompatible with the idea of seeds carried by birds, 

 since it was observed that flocks of alighting birds ranged themselves in long lines at or 

 near the water's edge in positions fairly correspondent with those later occupied by ranks 

 of vegetation ; but nothing more definite may be said, in concluding the discussion of this 

 phase of the subject, than that one species was found where it must have been carried by 

 birds, another near nests in positions which it might have reached by wind or flotation, 

 and that 32 others had seeds liable to be carried about by adhesion to the limbs or plumage, 

 or in the crops. 



In the transportation of seeds and plants which finally lodged on the sterilized areas 

 flotation played a part much more important in the Salton region than in any other region 

 that has yet been studied, paradoxical as this may seem in a desert region. Furthermore, 

 the number of instances in which seeds and plants could have been introduced by water 

 only are fairly large. Among these are to be included the deposition of rootstocks of 

 Typha, of rhizomes of Phragmites, of a living branch of Prosopis glandulosa, of stems of 

 Distichlis, and of fruits of Cucurbita on various beaches, while the tubers of Scirpus palu- 

 dosus are readily moved in this manner. 



The species tested in the Laboratory may be taken as offering the general conditions 

 of the entire lot of plants with which this paper is concerned. Reference to previous pages 

 will confirm the statement that Atriplex lentiformis does not sink, but the floating seeds 

 germinate within a few days on the surface. Juncus floats 37 days, then germinates 

 quickly after sinking. Leptochloa germinates 78 days after being wetted and while still 

 afloat. Sesuvium remains afloat 23 to 50 days, then sinks and germinates. Rumex seeds 

 float only 3 days when stripped, but supported by the calices or other parts of the inflores- 

 cence may remain afloat until germination ensues. Isocoma remains afloat less than a 

 month. Oligomeris remains afloat about 60 days and germination ensues, both at surface 

 and among the sunken ones to some extent. Amaranthus floats 30 days, then the seeds 

 sink and a few germinate within the next fortnight. Baccharis floats less than a month and 

 Pluchea about the same length of time. Spirostachys sinks within a day and begins germi- 



