284 PBAGTIGAL BOTANT. 



983. Achenia winged and sometimes also 2-toothed, 

 Heads corymbed, or nearly solitary. Tall rough herbs. 

 Lower leaves sometimes whorled in threes. Silphimn. 



Achenia flattened. Heads always single, long- 

 peduncled. A hairy, low herb (2-6 inches high). Flowers 

 yellow. Leaves ovate or spatulate, crenate, long-petioled. 

 Chrysogonum Virgiuianuia, L. 



984:. Achenia compressed laterally, or not at all 986 



Achenia compressed back and front 985 



985. Achenia with upwardly barbed awns, or awnless, 

 never beaked. Rays yellow, or partly colored, rarely 

 purple. Coreopsiis. 



{Tickseed.) 

 Achenia with retrorsely hispid awns, often attenu- 

 ated above. Bidens. 



{Bur-Marigold. ) 



986. Achenia wingless. Awns deciduous. Heads soli- 

 tary or corymbed. (980) Helianthus. 



Achenia broadly winged. Awns persistent. 



(980) Actiuomeris. 



987. (904.) Pappus present 988 



Pappus none. Involucre cylindric, of 8 scales, in 



a single row, 8- to 12-flowered. Heads small, loosely pani- 

 cled; flowers yello\,r. Leaves angled, or toothed, ovate, or 

 sometimes lyre-shaped. Xiampsana commums, L. 



(Nipple-wort) 



988. Pappus of plumose bristles, which are chafiy- 

 dilated at the base, either on a short beak, or sessile. Scapes 

 bearing one or more yellow heads. The radical leaves pin- 

 natifid. Leoutodon autuiuuale, L. 



Pappus not plumose 989 



989. Pappus chaffy, or of both chaff and bristles. . .990 

 Pappus composed exclusively of capillary bristles. 



992 

 99©. Rays yellow. Pappus double. Heads terminating 

 the naked scapes, or branches. Leaves chiefly radical. . . 991 

 Rays blue. Pappus a small crown of little, bristle- 

 form scales. Involucre double. Heads large, 2 or 3 together, 



