(68 ) 
3. Evax.—Scales of the involucre 1-2 ser- 
iate. Pappus 0. 
4, Filago.—Scales of the involucre imbri- 
cate. Pappus pilose. 
III, Frustranea. 
Corethrogyne.—Receptacle naked. 
Centaurea.—Receptacle bristly. 
Bidens.—Pales of the receptacle decidu- 
ous. 
4, Helianthus.—Palez of the receptacle per- 
sistent. Pappus paleaceous, caducous. 
fo BS. 
5. Helianthella. Palew of the receptacle 
persistent. Pappus 2 persistent awns, 
besides the caducous palez. 
IV. Necessaria, 
A. Receptacle naked. 
a. Anthers obtuse at the base, at least not 
calcarate. 
aa. Branches of the style of the ? flowers 
flat and tipped with an appendia. 
1 Erigeron, 
bb. Branches of the style not flat, but 
tapering, sometimes with an appendia. 
1. Hemizonia. —Involucre 1-seriate, each 
scale with its base half embracing a ray 
akene. Pappus of ray 0. 
