440 



COMPOSITAE. 



[Vol. III. 



II. Bidens aristosa (Michx.) Britton. 



Western Tickseed-Sunflower. 



(Fig. 3948.) 



Coreopsis arislosa Michx. Fl. Bor. Am. 2: 140. 1803. 

 C. arislala Muhl, ; Willd. Sp. PI. 3: 2253. 1804. 

 B. arislosa liritton, Bull. Torr. Club, 20; 281. 1893. 

 Annual or biennial; stem much branched, 

 i°-3° high. Leaves thin, sleuder-petioled, pu- 

 bescent beneath, the lower ones pinnately 5-7- 

 divided, 3'-6' long, the segments lanceolate, 

 serrate, incised or pinnatifid, acuminate, nar- 

 rowed at the base; upper leaves less divided, 

 lanceolate, or merely lobed, sessile or short- 

 petioled; heads numerous, slender-peduncled, 

 i'-2' broad; outer bracts of the hemispheric in- 

 volucre linear or spatulate, usually ciliate, not 

 surpassing the inner; rays 6-9, obtuse; achenes 

 very flat, oblanceolate or obovate, upwardly 

 ciliate and strigosepubescent; pappus of 2 slen- 

 der upwardly or downwardly barbed awns, 

 nearly as long as the achene, rarely wanting. 

 In swamps and wet prairies, Illinois to Michigan, south to Louisiana and Missouri. Aug.-Oct. 



12. Bidens involucrata (Nutt. ) Brit- 

 ton. l,ong-bracted Tickseed-Sunflower. 

 (Fig. 3949.) 



Coreopsis invohioata Nutt. Journ. Phil. Acad. 7; 



74. 1834. 

 Bidens involucrata Britton, Bull. Torr. Club, 20: 



281. 1893. 



Similar to the two preceding species, minutely 

 pubescent, i°-3° high, much branched. Seg- 

 ments of the leaves narrower, linear-lanceolate, 

 incised or pinnatifid, long-acuminate; heads 

 numerous, i'-2' broad, on slender usually hispid 

 peduncles; outer bracts of the hemispheric in- 

 volucre linear-lanceolate, acuminate, densely 

 hispid and ciliate, much exceeding the inner 

 ones; rays orange at the base; achenes flat, 

 ciliate and strigose; pappus of 2 short teeth. 



In swamps, Illinois to Kansas, Arkansas and 

 Texas. July-Sept. 



13. Bidens Beckii Torr. Water 

 Marigold. (Fig. 3950.) 



Bidens Beckii Torr. ; Spreng. Xeue Entdeck. 2; 



135- 1821. 



Perennial, aquatic; stems simple, or little 

 branche<l, 2°-S° long. Submersed leaves 

 sessile, i'-2' long, repeatedly divided into 

 numerous capillary segments; emersed 

 leaves few, sessile, opposite, or sometimes 

 in 5's, lanceolate or oblong, acute, serrate or 

 laciniate, '/z'-l'/i' long; heads solitary or 

 few, shortpeduncled, i''-i,'2' broad; involu- 

 cre hemispheric, its bracts oval or oblong, 

 obtusish, glabrous, the outer somewhat 

 shorter than the inner; rays 6-10, obovate, 

 or oblong, obtuse, golden yellow; achenes 

 nearh' terete, each end truncate; pappus of 

 3-6 slender awns, downwardly barbed above, 

 smooth below, divergent, 6"- 12" long. 

 In ponds and streams, Quebec to New Jersey, west to Manitoba and Missouri. Aug.-Sei>t. 



