203. 
3. Sandy beach habitat; phyllaries of staminate 
involucre not united; fruiting head a very 
prickly bur, 2-seeded; leaves simple...............-. Xanthium 
3. Roadside and field habitat; phyllaries of 
staminate involucre united; fruiting head not 
burlike, 1-seeded; leaves lobed or dissected. 
(Also, staminate heads inverted)........+.+e+e+eeeees Ambrosia 
1. Ray flowers present. 
4. Disc flowers sterile; ray flowers fertile. 
Expected (Polymnia, Silphium, Parthenium). 
4. Disc flowers fertile; ray flowers fertile or 
sterile. 
5. Leaves decurrent down the stem. 
6. Ray flowers sterile; phyllaries bent 
downward, few; leaves pinnately 
veined; flowers pale yellow.........cceecceeeeeee ACtinomeris 
6. Ray flowers pistillate; phyllaries imbricated, 
many; leaves 3-nerved; flowers golden-yellow. 
sieheralcretetenstiore ateretelavetonetete teteteieliele ey abeleNatleyerchenstiele dislseijeme Verbesina 
5. Leaves not decurrent. 
7. Achenes turbinate, 5-angled. (Also, leaves 
opposite; rays white; disc yellow).......cccoee Galinsoga 
7. Achenes flat, 4-angled or, if 5-angled, 
subterete and slender. 
8. Receptacle conical to columnar; leaves 
alternate. (Also, rays orange; disc brown) 
Ododigdocc odddddudopodudoddod Go Candaadoo doo Mulaelsta 
8. Receptacle flat or slightly convex; 
leaves opposite in all genera collected 
or expected. 
9. Flowers white; chaff of receptacle 
bristly; pappus a minute bristly 
CLOWN 0/000) overoie oo: velo io vielevelols sivicisisje/ejsis sleletenepme eC kampical 
9. Flowers yellow; chaff of receptacle 
broader, flattish; pappus of teeth, 
deciduous scales, or wanting. 
