ASTERACEAE 



35 



y. Pappus Ql 



(x) Receptacle smooth mixta 



(>•) Receptacle duff] Anthemis 



(h) Leavei not strong-scented 



\. Pappus a I ion n, or none Ambrosia 



y. Pappus of two or more barbed awni Bidens 



2. Floweri of two kinds, tabular and ray, or all ray in doubled forms 



a. Heads with chaff, i. <-., each flowei with ■ stale 



(1) Ray flowers trumpet-shaped Centaur ea 



(2) Kay Bowers Bat, ribbon- or strap shaped 



(a) Kays white 



\. Leaves pinnately dissected, strong-scented Anthemis 



\. Leaves no) dissected or strong scented Galinsoga 



(b) Kays yellow or purple 



\. I»isk globose to cylindric 



^ \ ) Chaff stout or spiny; rays white, red or purple 

 m. Chaff equalling the disk flowers Zinnia 



a. Chaff much longer than the disk flowers Echinacea 



(y ) Chaff soft ; rays yellow 

 m. l>isk globose; achenes 4-anglcd Rudbeckia 



n. Disk oblong to cylindric; achenes wing-margined Ratibida 



y. Pisk Hat or slightly convex 



(\) Bracts of the involucre united, at least one series 

 m. Chaff broad ; achenes flat, winged-margined Dahlia 



n. C'halT linear or long pointed ; achenes not flat or winged 



(m) Kays white to pink or red Cosmos 



(n) Kays yellow to maroon 



r. Pappus teeth barbed upward or downward Bidcns 



s. Pappus teeth smooth or lacking Coreopsis 



(y) liracts not united, or somewhat so at base 

 m. Achenes broad, winged 



(m) Rays in 2-.? rows; disk flowers sterile Silphium 



(n) Kays in 1 row; disk flowers fertile I'crbesina 



n. Achenes not winged 



(m) Kays neutral, deciduous 



r. Pappus of two triangular awns ; achenes 4-angled Helianthus 



s. Pappus of two awns and small scales; achene flat 11 ' elianthclla 



(n) Kays pistillate, persistent ; pappus crown like Hdiopsis 



b. Heads without chaff; the receptacle slightly bristly in one or two cases 



(1) Pappus of capillary bristles 



(a) Rays yellow 



x. Heads small, 2-8 mm. SolidagO 



y. Heads larger, 1-3 cm. Chrysopsis 



(b) Kays white to blue or purple 



x. Heads single, on short scapes Bcllis 



\. Heads several-many 



(x) Rays narrow and many; bracts in 1-3 rows Erigeron 



(y) Rays broader and fewer; bracts in 3-5 rows 

 m. Pappus double; cultivated annual Callistephus 



n. Pappus single ; native 



(m) Heads in a panicle Aster 



(n) Heads in a cymose cluster Doellingera 



(2) Pappus none, or of 5-12 scales or bristles 

 (a) Pappus none 



x. Achenes of disk small and aborted Calendula 



