228 THE FLORA.. 



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. Eeoep- 

 taole chafify, flat. Aohenia flattened or 4-sided, crowned with 2-4 awns 

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



* Eays inconspicuous or none a 



* EayB quite showy, yellow 4, 5 



a Acheuia flattened, broadest at top 1-3 



a Aclienia slender, 4-Bided 6, 7 



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



2 B. oonna'ta. Leaves simple, lower ones sometimes 3-parted. Eays 0. 



3 B. oer'nua. Nodding B. Leaves simple, scarcely connate. Eays few or 0. 



4 B. clir7saiithemoi'des. Mud, B. Lvs. narrow-lanoe., equally serrate, connate. 



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



6 B. lenoan^tha. White B. Heads small, with white rays. Lvs. pinnate. S. 



7 B. bipiuna'ta. Spanish Needles. Eays very short, yellow, Lvs. bi-pinnate. 



4. OOEEOP'SIS. Tick-seed. 



Involucre many-flowered, double,, each of 8-13 scales, the outer leafy, 

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

 Achenianattened, often winged, emarginate, each commonly with 2 teeth 

 or awns which are not hispid downwardly as in Bidbns. — Leaves gener- 

 ally opposite. Heads showy (rarely without rays). 



* Heads discoid (without rays) 1, 2 



* Heads radiate, rays showy. . . .a 



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



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



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



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



b Leaves petiolate, compound, with lanceolate, toothed divisions. . . .8-5 



b Leaves petiolate, compound, with linear, entire divisions. . . .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. . . .11-13 



1 O. dlscoi^dea, Bayless T. Leaves on long petioles, ternateiy divided. W. 



2 0. bidentoi''des. Leaves on short petioles, toothed, lance-linear. Peffla. r. 



8 0. an'rea. Golden T. Leaflets 3-5. Outer scales about 8. AcherAa 2-4-toothed. S. 



4 0. trichosper'ma. Leaflets 6-7. Outer scales about 8. Ach. slender, 2-toothed. 

 6 O. aristo'sa. Leaflets 5-7. Outer scales 10-18. Achenia 2 or 4-awnod. W. 



6 0. trip'teris. Stem 4^8f. high. Hds. on short stalks. Eays J' long, entire. W. S. 



7 0. grancliflo'ra. St. l-2f. high. Heads on long stalks. Eays V long, 4-5-oleft. S. 



