ORDER 70. ASTERWORT8. 239 



3. BI'DENS. Burr-Marigold. 



Involucre scales nearly equal, double, the outer generally large and 

 leafy. Kays few (3-8, or sometimes none), neutral, disk perfect. Recep- 

 tacle chaffy, flat. Achenia flattened or 4-sided, crowned with 2-4 awne 

 which are hispid backwards. Leaves opposite. July- Oct. 



* Kays inconspicuous or none a 



* Rays quite showy, yellow 4, 5 



a Achenia flattened, broadest at top 1-3 



a Achenia slender, 4-sided. . . .6, 7 



1 B. frondo'sa. Leafy B. Leaves pinnately 3-5-fol., divisions distinct. Eays 0. 



2 B. conna'ta. Leaves simple, lower ones sometimes 3-parted. Kays 0. 



3 B. cer'nua. Nodding B. Leaves simple, scarcely connate. Kays few or 0. 



4 B. chrysanthemoi'des. Mud B. Lvs. narrow-lance., equally serrate, connate. 



5 B. Beck'ii. Beck's B. Lvs. mostly under water and very finely divided. M. 



6 B. leucan'tha. White B. Heads small, with white rays. Lvs. pinnate. S. 



7 B. bipinna'ta, Spanish Needles. Kays very short, yellow. Lvs. bi-pinnate 



4. OOREOP'SIS. Tick-seed. 



Involucre many-flowered, double, each of 8-1 3 scales, the outer leafy, 

 the inner membranous. Receptacle flat, the chaff falling with the fruit. 

 Achenia flattened, often winged, emarginate, each commonly with 2 teeth 

 or awns which are not hispid downwardly as in BIDKNS. Lea38 gener- 

 ally opposite. Heads showy (rarely without rays). 



* Heads discoid (without rays) 1, 2 



* II ads radiate, rays showy. . . .a 



Disk yellow, rays also yellow, mostly entire.... b 



Disk yellow, rays rose-colored, 3-5-toothed at the end. . . .20, 21 



Disk purple, rays yellow with a purple base, toothed 18, 19 



Disk purple, rays wholly yellow, toothed at the end 14-17 



b Leaves petiolate, compound, with lanceolate, toothed divisions 3-5 



b Leaves petiolate, compound, with linear, entire division's 6, 7 



b Leaves petiolate, simple, or some of them eared at base 8-10 



b Leaves sessile, 3-parted, divisions entire or not often, seeming whorled . . . .11-lt 



1 C. discoi'dea. Eaylest T. Leaves on long petioles, ternately divided. W. 



2 C. bidentoi'des. Leaves on short petioles, toothed, lance-linear. Penn. r. 



C au'rea. Golden T. Leaflets 3-5. Outer scales about 8. Achenia 2-4-toothed. S. 



4 C. trichosper'ma. Leaflets 5-7. Outer scales about 8. Ach. slender, 2-toothed. 



5 O. aristo'sa. Leaflets 5-7. Outer scales 10-13. Achenia 2 or 4-awned. W. 



6 C. trip'teris. Stem 4-8f. high. Hds. on short stalks. Kays 4' long, entire. W. 8 



7 C. grandiflo'ra. St. l-2f. high. Heads on lonsj stalks. Rays 1' long, 4-5-eleft. S 



