COMPOSITAE (THISTLE FAMILY) 



30 a Wild herbs 2. Eupatorium. p 227 



b Cultivated herbs 31 



31 a Leaves ovate to heart-shaped; styles much longer than 



the corolla 4. Ageratum. p 227 



b Leaves lanceolate to oblong; styles not longer than the 



corolla 3. Piqueria. p 227 



32 a Achenes crowned by a pappus of 2-4 barbed awns 



44. Bidens. p 236 

 b Achenes not crowned by a pappus . . 30. Polymnia. p 234. 



33 a Flowers yellowish or orange 34 



b Flowers not yellowish or orange 36 



34 a Wild herbs; pappus of 2-4 stiff, barbed awns 



44. Bidens. p 236 

 b Cultivated herbs; pappus not of barbed awns 35 



35 a Heads Vi-i in. broad; leaves clasping at the base 



29. Emilia, 

 b Heads 1-4 in. broad; leaves not clasping at the base 



28. Gaillardia. p 234. 



36 a Plant with sticky hairs, with a camphor-like odor, 



growing in salt marshes 22. Pluchea. p 233 



b Plants not completely as in a 37 



37 a Heads %-x in. broad 15. Erigeron. p 233 



b Heads M> in. or less broad 38 



38 a Flowers usually purplish; pappus purplish 



i. Vernonia. p 227 

 b Flowers white, green, or pink; pappus whitish 39 



39 a Lower leaves lanceolate or ovate lanceolate; involucre 



swollen at the base especially before flowering 



56. Erechtites. p 238 



b Lower leaves triangular-lanceolate or arrow-shaped; 

 involucre not swollen at the base 



57. Synosma. p 238 



40 a Leaves wanting at flowering time; flowering stalk with 



alternate bracts; flowers yellow.. 54. Tussilago. p 238 

 b Leaves present at flowering time 41 



41 a Leaves basal ; plant cultivated for the flowers 



ii. Bel Us. p 230 

 b Leaves not all basal 42 



42 a Some or all of the stem leaves opposite 43 



b Stem leaves all alternate 60 



43 a Upper leaves united at their bases to form a cup-like 



disk 31. Silphium. p 234 



b Upper leaves not united as in a 44 



44 a Irregular or ray flowers very numerous, in several rows; 



plants cultivated for the flowers 45 



b Irregular or ray flowers usually in i or 2 rows, usually 



less numerous than the regular or disk flowers 47 



223 



