274 CICHORIACEAE 



Achenes S-ribbed; main bracts scarious-margined: receptacle 



bristly. 11. Calycoserls. 



Achenes 10-striate; bracts not scarious; receptacle not bristly. 



12. YOUNGI.\. 



Achenes 5-ribbed, conspicuously cancellate-sculptured, with a cupu- 

 late shoulder, from wliich the slender, 5-ribbed hollow beak 

 arises. 13. Glyptoplura. 



Achenes not beaked, columnar, 5-15-ribbed, truncate at the apex. 



Involucres of broad silvery-scarious bracts, regularly imbricate; 



bristles of the receptacle persistent. 14. ^MALACOLEprs. 



Involucres of narrow acuminate or acute bracts, only slightly scari- 

 ous-margined; bristles of the receptacle, if any, few and decidu- 

 ous. 15. Malacothrix. 

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

 the brealcing off of the beak. 

 Beak of the achenes none or a mere attenuation. 

 Flowers rose or purpUsh. 



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

 the summit. 16. Pleiacanthus. 



Plants not spiny. 



Stems rush-Like and striate; leavas narrowly linear-lanceolate 

 or reduced; achenas tapering at the surrimit. 



17. Lygodesmia. 

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

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



IS. Prenanthella. 

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

 terete or 4-5-angled. 19. Nab.\lus. 



Flowers yellow or white. 



Heads several, rarely solitary; stem leafy. 

 Achenes tapermg upwards; pappus white. 



Achenes not dilated into a pappiferous disk. 



Bracts in fruit more or less tliickened at the base or 



on the midrib. 20. Crepis. 



Bracts not tliickened on the backs. 



21. Heteropleur.a. 

 Achenes contracted into a more or less distinct beak. 

 enlarged at the apex into a pappiferous disk. 



12. YOUXGTA. 



Achenes not tapering upwards; pappus in ours sordid or 

 reddish; bracts not tliickened. 

 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 sohtary on a leafless scape. 10. Nothocalais. 



Beaks of the achenes distuict and slender; plants scapiferous. 



Achenes 10-ribbed or 10-nerved, not spinose-miu-icate; involucres 



more or less imbricate. 23. Agosekis. 



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; leafv-stemmed plants with paniculate heads. 



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



involucres cvUndraceous. 25. Lactuc.\. 



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

 nection; involucres hemisplierical or campanulate. 2G. Sonchus. 



1. ATRICHOSERIS A. Gray. i. a. platyphuUu. 



2. PTILOCALAIS Greene. 



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.o cm. high. 



1 . P. major. 

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



2. P. nutans. 

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



Pappus-squamellae Uuear-lanceolate, gradually tapering into the awn. 



Leaves Unear-lanceolate or lanceolate; squameUae 4-5 mm. long. 4. P. macrolcpis. 

 Leaves narrowly linear; squameUae 2 mm. long or less. 5. P. tenmfolia. 



3. PTILORIA Raf. Desert Pixk, Flowering Straw. 



P p r Gurii 3( Is 



Heads 10-20-flowered; involucres over 1 cm. lugh; leaves broad, runcinate, with short 



lobes. 1- P- Parryi. 



Heads 3-9- (mostly 5-) flowered. 



Pappas plumose to the base; involucres 7-10 mm. high. 



Leaves verv narrow, almost filiform and iLsually entire. 2. P. tcnuifoha. 



