MOVEMENTS OP 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. 



Practically 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 around 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 Strands of Salton Sea. 



Amaranthus palmeri 

 Aster exilis var. australis 



spinosus 

 Astragalus limatus 

 Atriplex canesoens 



fasciculata 



hymenelytra 



lentiformis 



linearis 



polycarpa 

 Baccharis glutinosa 

 Bouteloua arenosa 

 Chamsesyce polycarpa Iiirtella 

 Chenopodium murale 

 Coldenia plicata 

 Conyza coulteri 

 Cryptanthe barbigera 

 Cueurbita palmata 

 Cyperus speciosus 

 Eclipta alba 



Eleocharis sp. 

 Encelia eriocephala 



frutescens 

 Eriogonum plumatella 



thomassii 

 Franseria dumosa 

 Heliotropium curassavicum 

 Hilaria rigida 

 Hynienoehloa salsola 

 Isocoma veneta var. acradenia 

 Juncus cooperi 

 Lepidium lasiocarpum 

 Lippia nudiflora 

 Leptochloa imbrieata 

 Oenothera scapoides aurantiaca 

 Oligomeris glaucescena 

 Olneya tesota 

 Parosela emoryi 

 spinosa 

 Phragmites communis 



1'luchea camphorata 



sericea 

 Polypogon monspeliensis 

 Populus macdougalii 

 Prosopis glandulosa 

 pubescens 

 Psathyrotes ramosissima 

 Rumex berlandieri 

 Salix nigra 

 Scirpus americanus 



olneyi 



paludosus 

 Sesuvium sessile 

 Sonchus asper 



oleraceus 

 Sphajralcea orcuttii 

 Spirostachys occidentalis 

 Suaeda torreyana 

 Typha angustifolia 

 Wislizenia refracta 



