270 GONTKIBUTIONS FROM THE NATIONAL HERBARIUM. 



Flowers purple or deep purplish. Plants more or less pubescent. 

 Leaves with numerous small glands beneath; pappus white, in 



one series, soft 19. PLTJCHEA. 



Leaves without conspicuous glands beneath; pappus purplish or 



yellowish, in 2 series, stiff 1. VERNONIA. 



Flowers white, whitish, or pale pink. 



Bracts finely pubescent; pappus bristles plumose, brownish; 



leaves finely gland-dotted beneath 5. KTJHNIA. 



Bracts glabrous; pappus bristles smooth or nearly so, white; 

 leaves not gland-dotted beneath. 

 Bracts usually 5 (some small ones usually present also at the 

 base of the involucre); flowers usually 5 in each head; leaves 

 often pale beneath, usually as broad as long. 



44. MESADENIA. 

 Bracts 12 or more; flowers 20 or more in each head; leaves green 

 on both sides, longer than broad. 

 Leaves with 2 very acute lobes at the base; bracts about 1 cm. 



long; plants perennial 45. SYNOSMA. 



Leaves tapering at the base; bracts about 1.5 cm. long; plants 



annual 43 . ERECHTITES . 



AA. Outer flowers of the heads produced into a strap-shaped ray (the ray sometimes 

 small), the corollas of the inner flowers with 5 equal lobes. 

 C. Leaves opposite or whorled, or the uppermost sometimes alternate. 



Stems winged. Rays yellow; leaves ovate, toothed 32. VERBESINA. 



Stems not winged. 



Rays pure white or purplish, small. Flower heads small; plants annual. 

 Leaves petioled, broadly ovate; pubescence of the stems spreading; achenes 



pubescent 35 . GALINSOGA . 



Leaves sessile, narrowly lanceolate; pubescence of the stems appressed; 

 achenes pubescent on the flat apex but glabrous elsewhere. 



28. ECLIPTA. 



Rays yellow, sometimes pale but never white. 



Bracts in 2 distinct series, the inner ones usually thin, brownish or yellowish, 



the outer ones green, often leaflike. 



Plants with a tuft of basal leaves at flowering time; petioles usually longer 



than the blades: bracts 10, 5 in each series; plants densely soft-hairy, 



perennial 25. CHRYSOGONUM. 



Plants without a tuft of basal leaves at flowering time; petioles shorter 



than the blades or often Avanting; bracts more than 10; plants never 



densely soft-hairy. 



Pappus none or of 2 very short teeth; leaves each composed of 3 entire 



leaflets or else divided into numerous linear segments; glabrous 



perennials 33. COREOPSIS. 



Pappus of 2-6 barbed awns; leaves simple or pinnate, the blades or the 

 leaflets toothed, never linear; annuals or biennials, often pubescent. 



34. BIDENS. 



Bracts not in 2 distinct series, all alike or the outer ones gradually smaller. 

 Fruit covered with hooked spines. Annual with prostrate stems; leaves 



petioled, toothed; rays very small 23. ACANTHOSPERMTJM. 



Fruit never with hooked spines. 

 Leaves (except sometimes the uppermost) deeply lobed; plants tall 

 and coarse, with viscid pubescence. Fruit glabrous, without 

 pappus; rays large or very small 22. POLYMNIA. 



