1016 C1CHORIACEAE 



b Pappus persistent, tardily falling off, separately, or together only by 



the breaking off of the beak. 

 Beak of the achenes none or a mere attenuation. 

 Flowers rose or purplish. 



Plants spiny and rush-like; leaves scale-like; achenes truncate at 

 the summit. 16. PLEIACANTHUS. 



Plants not spiny. 



Stems rush-like and striate; leaves narrowly linear-lanceolate 

 or reduced; achenes tapering at the summit. 



17. LYGODESMIA. 

 Stems not rush-like ; leaves ample ; achenes tapering to the base. 



Annuals; heads 4-5-flowered ; achenes with 45 strong ribs. 



18. PRENANTHELLA. 

 Perennials; heads 8-30-flowered (rarely less); achenes 



terete or 4-5-angled. 19. NABALUS. 



Flowers yellow or white. 



Heads several, rarely solitary; stem leafy. 

 Achenes tapering upwards ; pappus white. 



Achenes not dilated into a pappiferous disk. 



Bracts in fruit more or less thickened at the base or 



on the midrib. 20. CREPIS. 



Bracts not thickened on the backs. 



21. HETEROPLEURA. 



Achenes contracted into a more or less distinct beak, 

 enlarged at the apex into a pappiferous disk. 



12. YOUNGIA. 



Achenes not tapering upwards; pappus in ours sordid or 



reddish; bracts not thickened. 



Leaves simple and entire-margined or denticulate; inflor- 

 escence in ours more or less corymbiform; bracts 

 narrow, green. 22. HIERACIUM. 



Leaves divided or lobed; inflorescence thyrsoid-panicu- 



late; bracts broad and colored. 19. NABALUS. 

 Heads solitary on a leafless scape. 10. NOTHOCALAIS. 



Beaks of the achenes distinct and slender; plants scapiferous. 



Achenes 10-ribbed or 10-nerved, not spinose-muricate ; involucres 



more or less imbricate. 23. ACOSERIS. 



Achenes 4-5-ribbed, muricate-spinulose at least near the apex; in- 

 volucres of a single series of principal bracts and several or num- 

 erous calyculate ones below. 24. LEONTODON. 

 2. Achenes flattened; leafy-stemmed plants with paniculate heads. 



Achenes narrowed at the top or beaked; pappus-bristles falling separately; 



involucres cylindraceous. 25. LACTUCA. 



Achene truncate at the top; pappus-bristles falling off more or less in con- 

 nection; involucres hemispherical or campanulate. 26. SONCIIUS. 



1. ATRICHOSERIS A. Gray. 



Glabrous winter annuals of desert regions, acaulescent, with cymosely 

 branched scapes. Involucre of about 15 linear, acute bracts in a single series, 

 and several small calyculate ones at the base. Receptacle scrobiculate. Flowers 

 white or purplish; ligules 5-toothed at the truncate apex. Achenes oblong, with 

 corky-thickened pericarp, S-10-ribbed, the alternate ribs thicker. Pappus none. 



1. A. platyphylla A. Gray. Leaves rcsulate-tufted at the base, sessile, 

 rounded-obovate, denticulate, with callous or spinulose teeth, 4-10 cm. long; 

 scape 3-6 dm. high, paniculately branched, with small bracts; involucres turbin- 

 ate, 6-8 mm. high; corollas white, with a purple base; ligules 10-12 mm. long. 

 Gravelly deserts: s Calif. s Utah w Ariz. Ap-Je. 



2. PTILOCALAIS Greene. 



Perennial herbs, with fusiform roots. Heads solitary at the end of the branches. 

 Involucres cylindric, of 8-12 bracts, in 1 or 2 series, and a few small calyculate 

 ones at the base. Receptacle with narrow scarious paleae. Corollas yellow. 

 Achenes 8-10-ribbed, columnar, linear, truncate at the apex. Pappus of 15-20 

 white soft plumose bristles with paleaceous bases. 



Pappus-squamellae oblanceolate or oblong, truncate or abruptly contracted into the awn. 

 Leaves entire or with short lobes. 



Leaf-blades proper lanceolate or elliptic; heads about 2.5 cm. high. 



1. P. major. 

 Leaf -blades proper linear or linear-lanceolate; heads less than 2 cm. high. 



2. P. nutans. 

 Leaves with long filiform lobes. 3. P. graciloba. 



