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3. Matricaria.—Receptacle cylindrical, hol- 
low. 
4. Baccharis.—Dicecious. 
b. Receptacle paleaceous or setaceous. 
aa, Branches of style connected near the 
apex, 
1. Cnicus.— Receptacle densely bristly. 
Bristles of the pappus plumose, con- 
nected at the base into a deciduous ring. 
Filaments of stamens distinct. 
2. Silybum.— Receptacle densely bristly. 
Bristles of pappus not plumose, 1-seri- 
ate. . 
3. Carthamus.—Pappus 0. 
4, Centaurea.—Receptacle densely bristly. 
Bristles of pappus not connected at their 
base into a ring. 
bb. Branches of style entirely distinct. 
1. Bidens.— Involucre 2-seriate, external 
spreading, internal erect. Pappus of 
2-4 awns. 
2. Madia.—Pappus 0. Receptacle some- 
times only paleaceous near the ray and 
naked at the disc. 
II. Superfiua. 
A. Receptacle naked. 
a. Anthers obtuse at their base, at least not 
calcarate. 
