(68) 



3. Evax. Scales of the involucre 1-2 ser- 

 iate. Pappus 0. 



4. Filago. Scales of tlie involucre imbri- 

 cate. Pappus pilose. 



in. Frustranea, 



1. Corethrogyne. Receptacle naked. 



2. Centaurea. Receptacle bristly. 



3. Bideiis. Palea3 of the receptacle decidu- 

 ous. 



4. Helianthus. Palese of the receptacle per- 

 sistent. Pappus paleaceous, caducous. 



5. Helianthella. Paleas of the receptacle 

 persistent. Pappus 2 persistent awns, 

 besides the caducous palese. 



IV, Necessaria, 



A. Receptacle naked. 



a. Anthers obtuse at the base, at least not 

 calcarate. 



aa. Branches of the style of the ? floioers 

 flat and tipped with an appendix. 



1 Erigeron. 



bb. Branches, of the style not flat, but 

 tapering, sometimes ivith an appendix. 



1. Hemizonia. Involucre 1-seriate, each 

 scale with its base half embracing a ray 

 akene. Pappus of ray 0. 



