COMPOSITE 401 



B. Fruit a completely closed and bur-like involucre, 

 containing 1 or 2 small akenes: flowers im- 

 perfect (see also No. 23). 



c. Involucre-bur large, and sharp-spiny 7. Xantliium 



cc. Involucre-bur small, not sharp-spiny 8. Ambrosia 



IB. Fruit not formed of a closed and hardened in- 

 volucre (although the involucre may be spiny, 

 as in Arctium and Cnicus). 

 c. Pappm none: akenes not awned. 

 D. The leaves opposite. 



E. Leaves simple: ttovver-heads small: flow- 

 ers blue or white 9. Ageratum 



EE. Leaves compound: flower-heads large, 



various colors, mostly of ray florets. 10. Dahlia 



EEE. Leaves dissected: heads showy 11. Cosmos 



EEEE. Leaves various: rays usually about 8, 

 neutral and yellow. (See Coreop- 

 sis 21). 

 DD. The leaves alternate. 



E. Foliage finely divided. 



F. Heads small (about K in.): akenes 



flattened 12. Achillea 



PF. Heads good - sized (about 1 in.): 



akenes oblong, angled or ribbed. 13. Anthem is 

 BE. Foliage leaves entire, toothed, or broad- 

 lobed. 

 F. Akenes curved or horse-shoe-shaped. 14. Calendula 

 FF. Akenes straight. 



G. Torus flat or slightly convex 15. Chrysanthemun) 



GG. Torus conical. 



H. Rays yellow: flowers large: 



2-3 in ]G. Rudbeckia 



HH. Rays not yellow: flowers abo.t 



lin. acriss: plant low 17. Bellis 



CO. Pappus of 2 thin early deciduous scales 18. Helianthus 



ccc. Pappus a short crown, or akenes awned at the 

 top with 2 (or more) awns, 

 n. Akenes angled or ribbed, crowned with cup- 

 like or loKed pappus: foliage strongly 



" tansy " scented 19. Tanacefum 



DD. Akenes more or less flattened, and awned 

 at summit, with usually 2 or 4 awns. 

 E. Awns barbed downward : akenes various, 

 narrowed at top, and awned, but 



not really beaked 20. Bidens 



EE. Teeth not downwardly barbed: (some- 

 times akenes awnless) 21. Coreopsis 



Z 



