280 PBACTIGAL BOTANT. 



955. Achenia very silky. Rays about 5, white. Leaves 

 linear _ or _ ample, somewhat serrate sometimes. Heads 

 small, in little clusters, forming a flat corymb. 



Sericocarpus. 

 Achenia not silky 956 



956. Eays 5-V5. Scales of the involucre (more or less) 

 loosely or closely imbricated," usually with leaf -like tips. 

 Achenia flattish. Aster. 



Rays 40-200, always white. Involucral scales 

 nearly equal, almost in a single row. Achenia flattened, 

 usually pubescent and 2-nerved. (953) Erigeron. 



957. Pappus simple ; the bristles equal or nearly so. 



958 



Pappus double, the outer set of bristles very small. 



Rays numerous, yellow. Herbs woolly or hairy, usually low. 



Heads rather large, often corymbed at the end of the 



branches. Chrysopsis. 



958. Scales of the involucre imbricated, the outer ones 

 shorter 959 



Scales of the involucre not imbricated, equal. 

 Pappus bright white, very soft. Heads solitary, or 

 corymbed ; flowers chiefly yellow. (921) Senecio. 



959. Either rounded-hea,rt-shaped (lower) leaves, and 

 small heads, or very large, showy heads, and anthers tailed 

 at the base. Flowers always yellow. Pappus never un- 

 equal 960 



Leaves never heart-shaped. Heads small. Pappus 

 sometimes slightly and irregularly unequal. Rays' (1-16) 

 usually yellow, rarely cream-color, or nearly white. Achenia 

 many-ribbed, nearly terete. Stems mostly wand-like. Heads 

 clustered, or i-acemed. Solidago. 



960. Heads corymbed, small, 8- to 10-flowered, racemed, 

 or spiked along the branches. Lower leaves rounded-heart- 

 shaped, upper ones ovate, all serrate. Pappus of minute, 

 scale-like bristles. Brachychseta cordata, Torr. & Gr. 



Heads solitary, large showy. Rays numerous. 

 Involucral scales ovate. Pappus scabrous. Anthei-s with ' 

 two bristles at the base. Inula Selenium, L. 



