1907] Hall. Compositae of Southern California. 273 



base ; these becoming callous-thickened. Flowers yellow. Achenes 

 obcompressed, ribbed, not beaked. Pappus copious, of cottony- 

 white exceedingly soft and fine hairs, mainly falling together. 



Leaves runcinately or lyrately pinnatifid into broad lobes, or sometimes 



only serrate. 

 Leaf -auricles mostly acute: achenes longitudinally ribbed; the intervals 



transversely rugose 1. S. oleraceus. 



Leaf -auricles mostly rounded: achenes longitudinally ribbed; the inter- 

 vals smooth 2. S. asper. 



Leaves pinnately parted into narrow lobes 3. S. tenerrimus. 



1. S. oleraceus L., Sp. PL 794 (1753). COMMON SOW-THISTLE. 

 A nearly simple-stemmed annual, 3 to 30 dm. high: leaves 



with the terminal segment commonly large and triangular, dentic 7 

 ulate or toothed; lower leaves petioled; uppermost sessile and 

 commonly lanceolate: peduncles occasionally glandular-hirsute: 

 involucre 8 to 16 mm. high: achenes longitudinally ribbed and 

 transversely rugose. 



Naturalized European weed : in waste places, flowering at all 

 seasons. 



2. S. asper (L.) Hill, Herb. Brit. i. 47 (1769). 8. oleraceus 

 asper L., Sp. PL 794 (1753). PRICKLY SOW-THISTLE. 



Very similar to the preceding, but the leaves sometimes undi- 

 vided and commonly clasping by an auricled base, the auricles 

 rounded ; margins spinulose-denticulate : peduncles often conspic- 

 uously hirsute with spreading gland-tipped hairs: achenes flat, 

 margined with a narrow wing and longitudinally ribbed; inter- 

 vals between the ribs smooth, but the ribs as well as the marginal 

 wing rugulose or serrulate. 



Naturalized European weed : very common. 



3. S. tenerrimus L, Sp. PL 794 (1753). 



Much branched, 3 to 10 dm. or less high, very leafy up to the 

 short-pedunculate heads : herbage glabrous : leaves oblong in out- 

 line, the linear or narrowly lanceolate lobes commonly cuspidate 

 and either spinulosely denticulate or entire: achenes longitudi- 

 nally striate and transversely rugose. 



Native of Europe ; introduced at San Diego, and on San 

 Clemente, Santa Catalina, and San Nicholas islands. Mr. Bran- 



