THE WEEDS OF CALIFORNIA 493 



was common and the Lippia covered great stretches and here it 

 is used quite effectively to cover banks and waste places. 



In Los Angeles, south of Santa Barbara, I observed Erigeron 

 canadensis, Datura Tatula and a great deal of D. meteloides, 

 Franseria sp., Lactuca Scariola, Melilotus alba, Xanthium can- 

 adense, Radish (Raphanus sativus), Iowa Tumbleweed {Amar- 

 anth us graccizans), Pigw r eed (A. retroflexus) , Convolvulus 

 arvensis, Brassica campestris, Sorghum lialepense, Marrubium 

 vulgare, TJrtica holosericea, Ricinus communis, Nicotiana glauca, 

 Solanum nigrum, Helianthus animus, Dill (Anethum grave- 

 olens). 



The San Diego region in the extreme southern portion of 

 California is much more arid than Los Angeles, where irriga- 

 tion is practiced. A number of northern weeds occur. "We 

 note, however, that in waste places, there is an abundance of 

 Nicotiana glauca and N. attenuata and some Ricinus communis, 

 Digitaria sanguinalis and Setaria glauca though Digitaria and 

 Setaria are nowhere abundant in California. Erigeron can- 

 adense, Xanthium canadense, Amaranthus graecizans, Chenopo- 

 dium album, Avena fatua, Helianthus annuus, Polygonum 

 avicidare, Hordeum murinum, Plantaga lanceolata, Cosmos 

 bipinnatus, Cucurbita foetidissima are some of the other weeds 

 which occur in southern California. There is a great deal of 

 Datura meteloides as well. 



A list of weedy plants might be greatly extended. The out- 

 standing fact is that many of the weeds like Salsola, Centaurea, 

 Raphanus, Beta, Daucus, Datura, Chenopodium and Hordeum 

 are European, while a relatively small number are of tropical 

 origin like Amaranthus, Nicotiana, Ricinus and Cosmos. The 

 conspicuous native weeds are Hemizoma, Gayophytum, Helian- 

 thus and Croton. It is a striking fact that so few of the peren- 

 nial native plants have become weeds. The seeds of most of the 

 weeds germinate during the rainy season and rapidly mature 

 their seeds, leaving the landscape seer and brown. The yellow 

 composites like Hemizonia, Grindelia are in strong contrast to 

 the dead annual grasses that mark the California landscape in 

 August. 



