IO42 ANALYTICAL KEY TO GENERA OF COMPOSITAE. 



kk Pappus a persistent irregularly cleft crown Engelmannia 982 



h At least the disk achenes not flattened. 



i Disk-flowers sterile; leaves very large and thin Polymnia 979 



ii Disk-flowers fertile; leaves smaller. 

 j Involucre of 4 large somewhat united outer bracts, and 6-15 



smaller inner ones Tetragonotheca 985 



jj Involucre of many ordinary bracts. 



k Fleshy seacoast plants; leaves spatulate, entire Borrichia 990 



kk Inland plants. 



/ Leaves pinnately dissected Anthemis 1014 



// Leaves ovate, serrate Heliopsis 984 



dddd Pappus capillary; receptacle not chaffy. 

 e Rays yellow. 

 / Involucral bracts in one series, rarely in two. 



g Leaves opposite Arnica 1022 



gg Leaves alternate or basal. 



h Head solitary on a bracted scape, appearing before the large orbicu- 

 lar leaves Tussilago 1021 



hh Heads solitary or numerous, appearing with or after the leaves. 



Senecio 1024 

 // Involucral bracts in 3-several series. 



g Lower and basal leaves cordate Brachychaeta 942 



gg None of the leaves cordate. 

 h Leaves bristly-serrate or pinnatifid. 

 i Achenes glabrous; pappus-bristles deciduous. 



Prionopsis (in Aphpappus) 93* 

 ii Achenes white-tomentose; pappus-bristles persistent. 



Sideranthus (in Aplopappus) 932 

 hh Leaves entire or toothed, not bristly-serrate. 

 i Leaves narrow, coriaceous, evergreen, entire; low western under- 



shrub Stenotus 933 



ii Leaves not evergreen. 



j Pappus double, the inner long, the outer of short scales or bristles. 

 k Achenes of disk flattened; ray-pappus obsolete. . . .Heterotheca 929 

 kk Achenes of both disk and ray flattened; ray-pappus present. 



Chrysopsis 929 

 jj Pappus single. 



k Heads very large, 5-10 cm. broad Inula 979 



kk Heads small, 0.5-2 cm. broad. 

 / Annuals; heads very loosely paniculate on long, slender pedicels. 



I sopappus (in Aphpappus) 933 

 II Perennials. 

 m Receptacles simply alveolate; rays few; panicles mostly 



dense Solidago 93J 



mm Receptacle fimbrillate; rays several or many; inflorescence 



more open, corymbose Euthamia (in Solidago) 94: 



ee Rays violet, purple, or white. 

 / Pappus-bristles very rigid and coarse. 

 g Achenes of the disk-flowers compressed, of the ray -flowers 3-angled; 



perennial herbs with large heads Townsendia 94 



gg Achenes fusiform, terete; annual herbs with small heads. 



Chaetopappa 

 ggg Achenes obovate, flattened, with thickened or winged margins; 



perennials Boltonia 94 



gggg Achenes turbinate, narrowed below, not winged. 



Machacr anther a (in Aster) 96 

 // Pappus-bristles soft and fine. 



g Involucral bracts in many series-, teeth or lobes of the leaves bristle- 

 tipped Machaeranthera 



gg Involucral bracts in 1-2 series, very narrow. 



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