1907] Hall. Compositae of Southern California. 85 



15. A. exilis Ell., Sketch ii. 344 (1824). SLENDER ASTER. 

 A slender erect annual, 3 to 10 or 12 dm. high, ending above 



in an open panicle: herbage glabrous: leaves glabrous, 6 to 12 

 dm. long and 3 to 6 mm. wide (or some of the lower ones 

 oblanceolate or oblong and 6 to 10 mm. wide), entire or rarely 

 serrate, those of the inflorescence lanceolate-subulate : involucre 5 

 or 6 mm. high; its bracts linear, acute, herbaceous, scarious- 

 margined : rays light-pinkish or purple, 3 mm. long : pappus fine 

 and soft. 



A common weed along river-bottoms and in waste or wet 

 places generally. Aug.-Oct. 



16. A. tanacetifolius HBK, Nov. Gen. Sp. iv. 95 (1820). 

 Machaeranthera tanacetifolia Nees, Ast. 225 (1832) ; Hook., Bot. 

 Mag. t. 4624 (1852). 



Erect, 2 to 4 dm. high: stem leafy, commonly simple below, 

 cymosely branched above, the ultimate branches terminated by 

 solitary showy heads: herbage finely pubescent: leaves 1.5 to 3 

 cm. long, oblong in outline, pinnately parted into few linear 

 widely spreading segments, or the lowest 2 to 3-pinnately parted, 

 some of the uppermost varying to linear and entire : involucre 

 8 or 9 mm. high; bracts linear-acuminate, the basal portion sca- 

 rious, the viscid-pubescent tips green : rays bright violet; 8 to 

 10 mm. long : achenes striate, canescently villous : pappus-bristles 

 rather rigid. 



Providence Mts., Cooper, ace. to Gray: thence east and south. 



A. PARVIFLORUS Gray, occurs in western Arizona and may 

 reach our borders. It is not so tall as A. tanacetifolius: herbage 

 glabrous but somewhat viscid : leaves simply pinnatifid, 2 cm. or 

 less long ; lobes very short : involucral bracts linear-oblong, with 

 ovate acute green tips: rays purple, 6 mm. long: achenes seri- 

 ceous : pappus soft, rather scant. 



17. A. canescens Pursh, Fl. ii. 547 (1814). Machaeranthera 

 Pinosa Elmer, Bot. Gaz. xxxix. 49 (1905). 



Plant 3 to 5 dm. high, from a biennial or perennial root : herb- 

 age minutely pubescent but usually green, inflorescence and in- 

 volucres glandular: lower leaves spinose-dentate, oblanceolate, 5 

 cm. or less long, including the winged petiole ; the upper becom- 



