1907] Hall. Compositae of Southern California. 11 



Involucral bracts narrowed above to a point, not closely imbri- 

 cated. 

 Principal leaves broadly lanceolate or wider: plant 4 to 7 dm. 



high: foothill canons 8. A. Greatai. 



Principal leaves narrowly lanceolate to linear. 



Plant 6 to 20 dm. high: heads numerous ...9. A. hesperius. 

 Plants 1.5 to 6 dm. high: heads rather few: mountains 

 above 1200 m. 



Leaves not sheathing: var. Parishii of 



10. A. Fremonti. 



Lower leaves sheathing the stem, elongated 



11. A. delectabilis. 



Stems leafless except at base, monocephalous : high-mountain species 

 12. A. Andersonii. 



Kays small and white or none : desert species with rush-like nearly leafless 

 stems (often woody at base). 



Achenes sericeous-pubescent: rays none 13. A. carnosus. 



Achenes glabrous: rays white, 3 mm. long 14. A. spinosus. 



B. Annuals and biennials: tips of involucral bracts erect: herbage 

 glabrous except in no. 16. 



Leaves entire or merely toothed 15. A. exilis. 



Leaves pinnately parted or cleft 16. A. tanacetifolius. 



C. Biennial or perennial: at least the outer involucral bracts with subu- 

 late recurved tips: herbage pubescent. 



Branching plant with showy heads in terminal cymes or panicles 



....17. A. canescens. 



1. A. tortifolius (T. & G.) Gray, Proc. Am. Acad. vii. 353 

 (1868) ; not A. tortifolius Michx., Fl. ii. 109 (1803) which is now 

 Sericocarpus tortifolius. Haplopappus tortifolius T. & G., Journ. 

 Bost. Soc. Nat. Hist. v. 109 (1845). Aster Mohavensis Coville. 

 Contr. U. S. Nat. Herb. iv. 126 (1893) ; not A. Mohavensis 

 Kuntze, Rev. Gen. 318 (1891). Xylorhiza torti folia Greene. Pitt, 

 iii. 48 (1896). MOHAVE ASTER. 



Woody at base, about 6 dm. high ; bark white : herbage tomen- 

 tose, at least when young: leaves linear to oblong, attenuate to a 

 sharp point, entire to incisely pinnatifid, the teeth or lobes com- 

 monly pungent : involucral bracts linear-attenuate, imbricated in 

 2 or 3 unequal series: rays about 40 to 60, lavender: achenes 

 white-villous : pappus of comparatively few rigid bristles, decid- 

 uous in a ring. 



