240 



KEY AND FLORA 



pollination. The genera of the northern United States are 

 divided into two suborders : I. Tubuliflor.e, corolla of 

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

 corollas all strap-shaped and flowers all bisexual. 



Fig. 30. Akenes with various types of pappus 



A, Rudbeckia, pappus wanting; B, Cichorimn, pappus a crown of fine scales; 

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

 conspicuous scales ; E, Cirsium, pappus a tuft of plumose hairs ; F, Lac- 

 tuca, pappus borne on a long beak 



I. TUBULIFLORJE 1 



Corollas some or all of them, tubular. 

 Rays w^iite, 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. 



