420 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Leaves densely covered with close matted white hairs on one or Isoth surfaces. 

 Flowering branches densely covered with very sticky hairs; hracts 4 or 5. 



12. ADENOCAULON. 

 Flowering branches without sticky hairs, or with a few but these hidden 

 under the other hairs and the stems not sticky to the touch; bracts 

 numerous. 



Leaves triangular, 10 to 20 cm. wide or larger 24. PETASITES. 



Leaves not triangular, much less than 10 cm. wide. 



Pappus none; leaves, at least some of them, toothed; heads mostly 2 to 3 



mm. broad 23. ARTEMISIA, 



Pappus of numerous soft bristles; leaves all entire; heads mostly more 

 than 3 mm. broad. 

 Plants not dioecious, the pistillate and staminate flowers in the same 

 heads; plants usually branched, annual or perennial; heads in 



dense clusters 11. GNAPHALITJM. 



Plants dioecious, the pistillate and staminate flowers on separate 



plants; plants with unbranched flowering stems, perennial; 



flowers mostly in racemes or loose clusters. 



Plants usually with clusters of leaves at the base, often with runners; 



leaves broad or narrow; pappus bristles of the pistillate flowers 



falling off in a ring 9. ANTENNABIA. 



Plants without clusters of basal leaves or runners; leaves linear or 

 linear-lanceolate; pappus bristles falling off separately. 



10. ANAPHALIS. 

 A A. t lower heads with rays. 



Rays not yellow, mostly white, blue, or purple. 



Leaves triangular, 10 to 20 cm. wide or larger 24. PETASITES. 



Leaves not triangiilar, much less than 20 cm. wide. 

 Leaves divided into numerous narrow lobes. 

 ■Flower stems naked; leaves palmately lobed; plants not strong-scented. 



•8. ERIGERON. 

 Flower stems leafy; leaves pinnately lobed; plants strong-scented. 



20. ACHILLEA. 

 Leaves entire or toothed or with only a few lolies. 



Pappus none; plants gla1)rous; rays white ... 22. CHRYSANTHEMUM. 

 Pappus of bristles or awns; plants glabrous or usually hairy; rays of various 

 colors. 

 Heads 3 to 4 mm. broad; rays very short and inconspicuous; plants 



annual 8. ERIGERON. 



Heads mostly 5 mm. broad or larger; rays long and conspicuous; plants 

 nearly all perennial. 

 Pappus of a few awns; stems each with a single head; bracts liroad, with 



thin whitish margins 6. TOWNSENDIA. 



Pappus of numerous soft bristles; heads 1 to many; bracts never with thin 

 whitish margins. 

 Bracts mostly linear-oblong or liroader; heads usually numerous. 



7. ASTER. 

 Bracts very narrowly linear; heads often solitary on the stem. 



8. ERIGERON. 

 Rays bright yellow. 

 Flower heads very sticky, with gland-tipped hairs or with a resinous secretion; 

 leaves alternate. 

 Leaves toothed; plants perennial; rays large and showy. . . 2. GRINDELIA. 

 Leaves entire; plants annual; rays very small and inconspicuous. 



17. MADIA. 



