272 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Pappus of a single series of long soft bristles; heads usually less than 

 7 mm. high, the rays much less than 1 cm. long; pubescence of the 

 leaves never of long appressed silky hairs. 

 Leaves all linear or nearly so, entire; flower heads in a flat-topped 

 corymb; receptacle of the flower head hairy or bristly; ray 

 flowers more numerous than the disk flowers. .10. EUTHAMIA. 

 Leaves, at least some of the lower ones, broader than linear, usually 

 toothed ; flower heads usually in a long narrow panicle or in a py- 

 ramidal panicle or in clusters in the axils of the leaves; receptacle 

 of the flower head usually pitted and not hairy or bristly; ray 

 flowers usually not more numerous than the disk flowers. 



9. SOLIDAGO. 



DD. Rays never yellow, usually white or purple. 



Leaves, at least most of them, divided nearly or quite to the midrib into 

 numerous lobes. Rays usually white; plants often strong-scented. 

 Heads very small, very numerous, on short stalks in dense corymbs, the 

 involucres about 3 mm. wide, the rays about 2 mm. long; perennials 

 with basal tufts of soft, much divided, plumelike leaves. 



37. ACHILLEA. 



Heads larger, usually solitary on long stalks, the involucres 6-15 mm. broad, 



the rays mostly 14-20 mm. long; annuals or perennials, never with 



basal tufts of soft plumelike leaves. 



Receptacles of the flower heads bearing numerous chafflike scales; 



plants annual or sometimes biennial, without basal tufts of leaves at 



time of flowering 38. ANTHEMIS. 



Receptacles of the flower heads naked, without scales; plants perennial, 

 usually with basal tufts of leaves at time of flowering. 



39. CHRYSANTHEMUM. 



Leaves entire or toothed, never lobed. 



Pappus of 2 or 3 very inconspicuous scales. Flower heads about 5 mm. 



broad, in a flat-topped corymb; rays white, very small; leaves broad, 



harsh to the touch, with short rough pubescence. 26. PARTHENIIIM. 



Pappus of numerous long slender bristles. 



Rays small, equaling or usually shorter than the diameter of the involucre, 

 not exceeding 3 mm. in length, white or tinged with pink. 

 Plants annual; leaves linear or nearly so; bracts linear, very acute. 



16. LEPTILON. 

 Plants perennial; leaves lance-oblong to obovate; bracts broader than 



linear, obtuse 9. SOLIDAGO. 



Rays large and showy, longer than the diameter of the involucre, usually 

 much more than 3 mm. long. 

 Bracts nearly equal in length, in one or 2 series, narrowly linear, very 

 numerous. Rays white, pink, or purplish; pappus bristles equal, 



in one series 15. EEIGERON. 



Bracts very unequal, the outer shorter, in several series, either broad 

 or, if very narrow, evidently broadest at the base. 

 Pappus bristles in 2 series, the outer ones shorter than the inner. 

 Rays white; leaves broader than linear... 13. DOELLINGEMA. 



Rays violet; leaves linear 14. lONACTIS. 



Pappus bristles in one series, equal or somewhat unequal. 

 Rays 4 or 5, white; involucres much longer than thick. Bracts 



broad, obtuse, cartilaginous IJ. SERICOCARPUS. 



Rays numerous; involucres usuallj^ nearly as broad as long. 



12. ASTER. 



