1592 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM 



Pappus awns or squamellae 4 or 5. 



Leaves densely tomentose or tomentulose beneath; heads 1 to 5, rather large 

 (about 1.8 cm. wide). 

 Leaves ovate, subcordate, densely canescent-tomentose beneath; heads 



solitary 14. C. grayii. 



Leaves ovate-oblong, not subcordate, very finely tomentulose beneath; 



heads about 5 15. C. discolor. 



Leaves green beneath; heads numerous, or if few, then small. 



Leaves small, the blades at most 2.5 cm. long, 7 mm. wide; heads few, small, 



in a naked terminal cymose panicle 16. C. brandegei. 



Leaves larger, 4 cm. long or more;' heads numerous. 



Leaves with conspicuous stipule-like auriculations at base. 



17. C. manicata. 

 Leaves without .stipule-like auriculations at base. 



Leaves oblong, 7.5 cm. wide, pilose on the nerves beneath. 



18. C. orizabaensis. 

 Leaves lanceolate or oblanceolate, 1.5 to 3.5 cm. wide, glabrous. 



20. C. pachyphylla. 

 Pappus awns or squamellae 7 to 20. 



Pappus awns as long as or longer than the achene. 

 Rays white or whitish, conspicuous. 



Phyllaries ciliate, otherwise essentially glabrous 8. C. integrifolia. 



Phyllaries rather densely pubescent dorsally. 



Leaves thickish, scabrous, green in drying 9. C. scabrifolia. 



Leaves thin, nearly smooth, blackening in drying. 



10. C. submembranacea. 

 Rays yellow or wanting. 



Heads 2 to 13, rather large; pedicels 3 to 10 cm. long. 



11. C. longipedicellata. 

 Heads numerous, rather small, umbellate-clustered, usually short-pedi- 

 celed or subsessile. 



Heads distinctly radiate 12. C. urticifolia. 



Heads discoid 13. C. trichotoma. 



Pappus awns or squamellae shorter than the achene. 



Leaves densely cinereous- or griseous-tomentose or -tomentulose beneath. 



Outer phyllaries without distinct herbaceous tips 4. C. pringlei. 



Outer phyllaries with conspicuous herbaceous tips. 



Leaves broadly ovate, about two-thirds as wide as long; pappus 



squamellae acutish 2. C. albida. 



Leaves suborbicular, about as wide as long; pappus squamellae obtuse. 



3. C. hypoleuca. 

 Leaves green and not densely pubescent beneath. 

 Pedicels mostly considerably longer than the heads. 



Heads discoid, 8 to 14-flowered 1. C. salmeaefolia. 



Heads radiate, with more numerous flowers. 



Leaves ovate, half as wide as long 19. C. rupestris. 



Leaves cuneate-obovate or oblanceolate, less than half as wide as 



long 20. C. pachyphylla. 



Pedicels mostly much shorter than the heads or obsolete. 



Leaves glabrous and not gland-dotted beneath 5. C. nelsonii. 



Leaves pubescent or gland-dotted beneath. 



Heads subcylindric, 4 or 5-fiowered 6. C. leptocephala. 



Heads turbinate or subcampanulate, 5 to 12-fiowered. 



7. C. zacatechichi. 



