COMPOSITE. 1 07 



36. Rudbeck la. Rays yellow, usually long ; disk dark-purple, or in 



one species greenish-yellow. Scales cf the involucre leaf -like. 

 Receptacle conical. Pappus none, or only a minute crown. 

 Ray-florets neutral. 



37. Ilelian thus. Rays yellow, neutral. Receptacle flattish or 



convex. Chaff persistent, and embracing the U-sided achenes. 

 Pappus deciduous, of 2 thin scales. Stout coarse herbs. 



38. Actinom'eris. Rays 2-8, irregular, yellow, neutral. Receptacle 



small, convex. Scales of the involucre few, soon deflexed. 

 Achenes flat, obovate, spreading when ripe. Pappus of 2 or 3 

 smooth awns, persistent. Tall branching perennials, with 

 mostly decurrent leaves. 



39. Coreop'sis. Rays mostly 8, yellow (sometimes brown-tinted), 



neutral. Receptacle flat. Involucre double, each of about 8 

 scales, the outer leaf-like and spreading, the inner rather 

 membranaceous and appressed. Achenes flat, compressed 

 parallel with the scales of the involucre, 2-toothed or some- 

 times naked. Heads corymbed. 



40. Gaillard'ia. Rays yellow (sometimes purplish), numerous. 3- 



cleft. Receptacle convex, the chaff bristly or awl-shaped. 

 Achenes top-shaped, 5-ribbed. Pappus of several long thin 

 scales, awn-tipped. Heads showy, fragrant, terminal, on scape- 

 like stems. N.W. 



41. Bidcns. Rays yellow, few; but 2 species are without rays. Scales 



of the involucre in 2 rows, the outer large and leaf-like. Ray- 

 florets neutral. Aohenes crowned with 2 or more stiff awns 

 which are barbed backward. 



42. Heliop'sis. Rays yellow, 10 or more, pistillate. Scales of the 



involucre in 2 or 3 rows, the outer leaf -like. Receptacle coni- 

 cal ; chaff linear, Achenes smooth, 4-angled. Pappus none. 



43. Achille'a. Rays white (occasionally pinkish), few. Receptacle 



flattish. Pappus none. Achenes margined. Heads small, in 

 flat corymbs. Leaves very finely dissected. 



44. Poly m ilia. Rays whitish-yellow, wedge-form, shorter than the 



involucre, few in number. Scales of the involucre in 2 rows, 

 the outer leaf-like, the inner small, and partly clasping the 

 achenes. Pappus none. Coarse clammy herbs with an un- 

 pleasant odour. 



4o. Sil phiuiii. Easily known by its stout square stem, and the 

 upper connate leaves forming a sort of cup. Flowers yellow. 

 Achenes broad and flat. 



