432 THE KINDS OF PLANTS 



A. Heads with all flowers strap-shaped (with rays) and 



perfect: juice milky: leaves alternate. 

 B. Flower-heads terminal on leafless, hollow stalk 



from radical leaves 1. Taraxacum 



BB. Flower-heads terminal on leafy stalks: leaves 



parallel-veined 2. Tragopogon 



BBB. Flower-heads in corymbs or clusters. 



c. Heads never yellow (usually blue or white): 



pappus of blunt scales 3. Cichorium 



cc. Heads usually yellow (in one. case blue). 



D. Achenes beaked: pappus copious, white, soft, 

 hair-like: leaves sometimes bristly or prickly 



edged 4. Lactuca 



DD. Achenes not beaked. 



E. Pappus soft, white: leaves usually auri- 

 cled and clasping at base, and prickly 



on edges and under ribs 5. Sonchus 



EE. Pappus stiff, brownish, leaves not spiny. . . 6. Hieracium 

 AA. Heads with tubular and mostly perfect disk flowers, 

 the rays, if any, formed of the outer strap-shaped 

 and imperfect flowers: in cultivated species, all 

 the flowers may become strap-shaped (head 

 "double"): juice not milky. 



B. Fruit a completely closed and bur-like involucre, 

 containing 1 or 2 small achenes: flowers im- 

 perfect (see also No. 23). 



c. Involucre-bur large, and sharp-spiny 7. Xanthium 



cc. Involucre-bur small, not sharp-spiny 8. Ambrosia 



BB. Fruit not formed of a closed and hardened in- 

 volucre (although the involucre may be spiny, 

 as in Arctium and Cnicus). 

 c. Pappus none: achenes not awned. 

 D. The leaves opposite. 



E. Leaves simple: flower-heads small: flowers 



blue or white 9. Ageratum 



EE. Leaves compound: flower-heads large, 



various colors, mostly of ray florets 10. Dahlia 



EEE. Leaves dissected: heads showy 11. Cosmos 



EEEE. Leaves various: rays usually about 8, 



neutral and yellow. (See Coreopsis, 21.) 

 DD. The leaves alternate. 

 E. Foliage finely divided. 



F. Heads small (about % in.): achenes 



flattened 12. Achillea 



FF. Heads good-sized (about 1 in.): achenes 



oblong, angled or ribbed 13. Anthemis 



