MOVEMENTS OF VEGETATION IN THE SALTON SINK. 



141 



theoretical rather than a practical one, since the upper layers of hills which became sub- 

 merged and then arose as an island from the receding waters had invariably been so 

 eroded and worn by the action of the waves that there remained but little question as to 

 the presence of any plant by invasion rather than by endurance of the flood in place. 



POSSIBLE INVADERS OF THE STRANDS. 



P*ractically all of the species inhabiting the Cahuilla Basin, including those native to 

 the alpine slopes of the San Jacinto Mountains, are to be included among the forms the 

 seeds of which might be carried by run-off streams, winds, or other agencies down to the 

 unoccupied areas aroimd the receding lake. The differences in climatic conditions and in 

 the soil, however, would obviously constitute an effectual barrier to the greater number 

 of the plants native to the rocky slopes of the mountains. Some of the barriers affecting 

 the dispersal of species on mountain slopes are much too subtle to be detected by available 

 methods of geographic survey. This is well illustrated by the cultures made at the Desert 

 Laboratory, in which many species abundant on the higher slopes of the Santa Catalina 

 Mountains in positions from which their seeds must have been carried to the lowlands in 

 myriads for centuries are not found below a certain limit, although when the seeds are 

 transported by man to the lower lands the plantlets survive and in some instances, such 

 as that of Juglans, outstrip the lowland species in vegetative activity. 



The species inhabiting the bajadas or detrital slopes of the basin, or of the lowermost 

 part included in the Salton Sink, would be the most important elements in any invasion 

 of surfaces left bare by the receding waters of the lake. The census of these forms is to be 

 found in the section of this paper compiled by Mr. S. B. Parish. 



A number of introduced species and weeds would constitute another element, and 

 plants of this kind would be carried along the line of the Southern Pacific Railroad, which 

 runs at varying distances from the shore of the lake for about three-fourths of its length. 

 The water actually washed the ends of the ties for many miles of the line at the maximum 

 level. It will be recalled also that a long stretch of the track previously ran below the 

 maximum level and was moved up the slope to evade the rising waters. 



The other element to be considered would be the species native to the valley of the 

 Colorado River. The entrance from this region would be principally by flotation. The 

 number of species included would be too large to be discussed in detail. Only those with 

 seeds which would be uninjured by long immersion would constitute potentialities in 

 invasion from this source. The census of the invasions from 1907 to 1912 inclusive includes 

 the following species: 



List of Species appearing on the Stratids of Salton Sea. 



Amaranthus palrneri 

 Aster exilis var. australis 



epinosus 

 Astragalus llmatus 

 Atriplex canescens 



fasciculata 



hyraenelytra 



lentiformis 



linearis 



polycarpa 

 Baccharis glutinosa 

 Bouteloua arcnoaa 

 Chamtcsyce polycarpa hirtella 

 Chenopodium murale 

 Coldenia plicata 

 Conyza coulteri 

 Cryptanthe barbigera 

 Cucurbita palmata 

 Cyperus speciosua 

 Eclipta alba 



Eleocharis sp. 

 Encelia eriocephala 



fruteseens 

 Eriogonum plumatella 



thotnassii 

 Franseria dumosa 

 Heliotropium curassavicum 

 Ililaria rigida 

 Hymenochloa salsola 

 Isocoma veneta var. acradenia 

 Juncus cooperi 

 Lepidiuin lasiocarpum 

 Lippia nudifiora 

 Leptochloa imbricata 

 Oenothera scapoides aurantiaca 

 Oligomeris glauceseens 

 Olneya tesota 

 Parosela emoryi 

 spinosa 

 Phragmites communis 



Pluchea camphorata 



sericea 

 Polypogon monspeliensis 

 Populus macdougalii 

 Prosopis glandulosa 

 pubescens 

 Psathyrotes ramosissima 

 Ilumex berlandieri 

 Salix nigra 

 Scirpus americanus 



olneyi 



paludosus 

 Sesuvium sessile 

 Sonchua asper 



oleraceus 

 Sphajralcea orcuttii 

 Spirostachya occidentalis 

 Suaeda torreyana 

 Typha angustifolia 

 Wislizenia refracta 



