IO4O ANALYTICAL KEY TO GENERA OF COMPOSITAE. 



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k Receptacle densely brist r ; corolla deeply lobed; involucral 



bracts fimbriate or dentate Centaurea 1034 



kk Receptacle naked; corolla dentate. 

 / Bracts of involucre in 2 series, outer shorter; leaves large; heads 



in involucrate glomerules Elephantopus 919 



// Bracts in 2-3-series, all nearly equal. 

 m Flowers 4-30 in the head. 



n Achenes 10-ribbed Trilisa 927 



nn Achenes, 5-angled Eupatorium 920 



mm Flowers 50-100; achenes 2-3-nerved. . Brachyactis (in Aster) 966 

 III Bracts of involucre in several series, outer shorter. 

 m Involucral bracts strongly striate-nerved; heads paniculate or 

 corymbose. 

 n Pappus-bristles rough or serrate; involucral bracts numerous. 



Coleosanthus (Brickellia) 924 

 ww Pappus-bristles plumose; involucral bracts few. .Kuhnia 924 

 mm Involucral bracts faintly if at all striate. 



n Heads spiked or racemose Lacinaria (Liatris) 925 



nn Heads corymbose. 



o Anthers tailed at the base Pluchea 973 



00 Anthers not tailed. 



p Pappus single Eupatorium 920 



pp Pappus double Vernonia 918 



cc Heads with ray and disk-flowers. 

 d Pappus composed of awns; rays yellow, white, or purple. 

 e Receptacle not chaffy. 



/ Heads 6 mm. broad Chaetopappa 944 



// Heads 20-35 mm - broad Grindclia 928 



ee Receptacle chaffy. 

 / Involucral bracts of 2 distinct sorts. 



g Bracts all separate or nearly so Bidens 1000 



gg Bracts of the inner series united to about the middle. Thelesperma 1003 

 // Involucral bracts of one sort, the outer merely shorter. 



g Receptacle convex or low-conical Verbesina 996 



gg Receptacle narrow-conical or cylindrical. 



h Rays 4 or 5, broad, persistent Crassina 983 



hh Rays 8-12, deciduous Spilanthes 985 



dd Pappus composed of scales. 

 e Receptacle chaffy. 

 / Rays white or nearly so, pistillate. 



g Leaves opposite Galinsoga 1004 



gg Leaves alternate Parthcnium 983 



// Rays bright yellow, neutral. 



g Involucral bracts of 2 distinct sorts Coreopsis 997 



gg Involucral bracts of 1 sort, the outer merely shorter. 

 h Leaves punctate, spatulate-linear. . ..Actinospermum (Baldwinia) 1004 



hh Leaves not punctate Helianthus 990 



ee Receptacle not chaffy. 

 / Rays purple, violet, or white. 



g Rays nearly entire, elliptical Boltonia 945 



gg Rays cuneate, 3-lobed, or cleft. 

 // [nvolucral bracts petal-like, colored, scarious at the tip. .Polypteris 1007 

 hh [nvolucral bracts not as above GaUlardia 1011 



// Rays yellow. 



g Plants dotted with oil-glands, especially the leaves and involucres. 

 h Involucral bracts more or less united; style-branches of the disk- 

 flowers elongated. 



i Bracts united only at the base Bocbcra (Dysodia) 1012 



ii Brai ts united high up into a cup Thymophylla 1012 



