240 KEY AND FLORA 
pollination. The genera of the northern United States are 
divided into two suborders: I. TusunirLtorm, corolla of 
the bisexual flowers tubular and 5-lobed; II. Liguriritora, 
corollas all strap-shaped and flowers all bisexual. 
Fic. 30. Akenes with various types of pappus 
A, Rudbeckia, pappus wanting; B, Cichorium, pappus a crown of fine scales; 
C, Coreopsis, pappus of 2 small scales; D, Helenium, pappus a crown of 
conspicuous scales; EL, Cirsium, pappus a tuft of plumose hairs; F', Lac- 
tuca, pappus borne on a long beak 
I. TUBULIFLORZ 1 
Corollas some or all of them tubular. 
Rays white, pink, or purplish. 
Rays many; akenes flat; pappus wanting; low herbs. Bellis, I 
Rays many; akenes cylindrical or winged, grooved; pappus 
wanting; tall herbs or shrubby. Chrysanthemum, X 
Rays many; akenes flat; pappus of an outer row of minute 
scales and an inner row of delicate bristles. Erigeron, II 
Rays many; akenes cylindrical or ribbed; pappus wanting; 
strong-scented, branching herbs. Anthemis, IX 
Rays few. Achillea, VIII 
1 The characters in this key are not necessarily true of all species in the 
genera referred to, but only of those described below. 
