KEY TO THE GENERA OF MANHATTAN PLANTS. 31 



29 Akenes not wing flattened 31 



30, Flattened radially; bracts few, nearly equal, re- 

 flexed Actinomeris 277 



80 Flattened tangentially, bracts numerous, in several 



rows iSilphium 279 



81. Receptacle conical or columnar . . 32 



81 . Receptacle flat or low convex 35 



32 Columnar; akenes flattened Lepachys 280 



32. Conical or short oblong; akenes 4-sided 33 



33. Chaff spiny-pointed, rigid, brown; pappus- toothed. . . ...Echinacea 281 



33 Chaff not rigid, spiny 34 



34. Leaves opposite; inner bracts coriaceous, appressed Heliopsis 282 



34. Leaves alternate; bracts all spreading Rudbeckia 283 



35. Bracts in 2 series, inner appressed-coriaceous, outer 



herbaceous, spreading 36 



35. Bracts not as above; pappus none or 2 deciduous teeth 37 



36. Pappus of 2 or more downwardly barbed spines Bidens 284 



36. Pappus none or of short teeth Coreopsis 285 



37. Bracts numerous, in several rows, akenes 5 mm or 



more Helianthus 286 



37. Bracts few or several; akenes 1 or 2 mm 38 



3S. Heads small, in corymbose clusters Achillea 287 



38. Heads medium, terminating the branches 39 



39. Leaves opposite; bracts foliaceous Eclipta 288 



39. Leaves alternate; bracts appressed, somewhat scarious.. Anthemis 289 



