240 



KEY AND FLORA 



pollination. The genera of the northern United States are 

 divided into two suborders : I. TuBULiFLOEiE, corolla of 

 the bisexual flowers tubular and 5-lobed; II. Ligulifloe^, 

 corollas all strap-shaped and flowers all bisexual. 



Fig. 30. Akenes with various types of pappus 



Rudbecfcia, pappus wanting; JB, Cichorium, pappus a crown of fine scales; 

 C, Coreopsis, pappus of 2 small scales ; D, Helenimn, pappus a crown of 

 conspicuous scales; E, C'irsium, pappus a tuft of plumose hairs; F, Lac- 

 tuca, pappus borne on a long beak 



I. TUBULIFLORiE 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, YIII 



1 The characters in this key are not necessarily true of all species in the 

 genera referred to, but only of those described below. 



