DUNE VEGETATION AT SAN FRANCISCO 195 



occur sparingly in low areas well covered with vegetation and 

 adjacent to traveled thoroughfares. Species of the following 

 genera were noted: Bromus, Festiica, Chcetochloa, Plaiitago, Lac- 

 tuca, Erigeron, Solanum. The greater extent of the dunes is, 

 however, without foreign plants of any kind. 



Annuals 



Very few annual plants were to be seen at the time of this 

 study (July- August, 1917) since such as occur in the area com- 

 plete their growth during the spring. The following native 

 annuals were, however, noted: Epilohium minutum, Epilobium 

 panicidatum, Chorizanthe pungens, Plantago patagonica cali- 

 fornica. Besides these native plants a nmiiber of the weeds 

 mentioned above are annuals, but as already suggested they are 

 of little importance and are almost entirely confined to low 

 ground with a w^ell-established plant cover or else occur in the 

 vicinity of dwellings or along roads. 



Plants of Sheltered Places 



Some plants are locally frequent, or even abundant, in shel- 

 tered stations, though the soil is not especially moist, viz.: 

 Eriogonum, Pentaccena, Cirsium, Eschscholtzia, Eriophyllum, 

 Polygonum, Castilleia. In the sheltered nooks, just as in places 

 of moderate exposure, the more abundant plants are yarrow, 

 pearly everlasting, dune tansy, Baccharis, Ericameria, lupines 

 and strawberry. The sand verbena and Franseria play here a 

 role far less conspicuous than in exposed situations. Toward 

 the eastern part of the area studied, where there is less wind 

 and less of shifting sand, the brake, blackberry and poison oak 

 occur. Still farther east one finds numerous weeds, and the 

 characteristic plants of dry hillsides beyond the limits of the 

 present study. 



Undermined and Burie^. Vegetation 



Such shrubby plants as willow, lupines and Baccharis are able 

 to withstand considerable undermining. The willow holds on ^^^-T^mT^ 



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