872 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



14. Plants not rushlike or spinescent; corollas yellow, rarely white 

 or flesh-colored (15). 

 15. Phyllaries somewhat thickened at base or on the midrib; 



pappus white 143. Crepis. 



15. Phyllaries not thickened; pappus dingy or brownish, or some- 

 times white 144. Hieracium. 



12. Achenes beaked (16). 



16. Pappus soon deciduous (17). 



17. Leaves not crustaceous-margined; plants conspicuously stipi- 

 tate-glandular above; achenes tapering into the beak, not 

 transversely rugulose 135. Calycoseris. 



17. Leaves crustaceous-margined; plants not stipitate-glandular; 



achenes abruptly beaked, transversely rugulose between 



the ribs 136. Glyptopleura. 



16. Pappus persistent (18). 



18. Achenes 10- to 15-ribbed or -nerved, not spinulose-muricate ; 



phyllaries imbricate in several graduated series (19). 

 19. Corollas rosy or whitish; phyllaries with conspicuous blackish 

 or brownish, scarious tips; pappus brownish. 



133. PlNAROPAPPUS. 



19. Corollas yellow or orange, sometimes turning purplish in age; 



phyllaries without dark scarious tips; pappus white or 



whitish 141. Agoseris. 



18. Achenes 4- or 5-ribbed, spinulose-muricate above; phyllaries 

 in 2 unequal series, the outer ones much shorter (20) . 



20. Plants scapose, the scapes naked, 1-headed; pappus whitish, 



without a woolly ring at base 137. Taraxacum. 



20. Plants caulescent, the stems more or less xeafy and branched; 

 pappus brownish, with a woolly ring at base. 



142. Pyrrhopappus. 



C. Hermaphrodite flowers with a tubular, regular or nearly regular corolla; rays 

 and pappus none or vestigial. 



1. Heads unisexual, monoecious; pistillate heads with 1 to 4 flowers enclosed in a 

 nutlike or burlike involucre, only the style tips exserted (2). 

 2. Phyllaries of the staminate heads separate; fruiting involucres burlike, 



covered with hooked prickles 51. Xanthium. 



2. Phyllaries of the staminate heads united (3). 



3. Pistillate involucre with several transverse scarious wings; leaves or their 



lobes linear-filiform 48. Hymenoclea. 



3. Pistillate involucre without transverse wings; leaves and their lobes not 

 linear-filiform (4). 

 4. Fruiting involucre unarmed or with a few teeth or tubercles in a single 



series below the beak 49. Ambrosia. 



4. Fruiting involucre with several or many spines in more than one series. 



50. Franseria. 

 1. Heads not unisexual; involucre not nutlike or burlike (5). 

 5. Flowers all hermaphrodite (6). 



6. Heads 1- or 2-flowered, aggregated in dense glomerules (7). 



7. Phyllaries of the individual heads connate into a toothed tube; leaves 

 ovate, petioled 38. Lagascea. 



7. Phyllaries of the individual heads separate; leaves lanceolate, sessile 



or subsessile 87. Flaveria. 



6. Heads many-flowered, not in glomerules (8) . 



8. Receptacle chaffy (9) . 



9. Inner phyllaries united at base into a cup; achenes thickish, papil- 

 late 74. Thelesperma. 



9. Inner phyllaries not united; achenes strongly compressed, very flat, 

 not papillate (10). 



10. Achenes strongly ciliate on the margin 64. Encelia. 



10. Achenes not e violently ciliate 65. Simsia. 



8. Receptacle not chaffy (11). 



11. Achenes strongly compressed 84. Laphamia. 



11. Achenes plump (12). 



12. Phyllaries with conspicuous whitish or yellow tips and margins; 

 achenes strongly 4- or 5-angled, usually hirsute on the angles. 



90. Hymenopappus. 



