CO M POSIT A E. IOC I 



numerous, short-peduncled, erect, 4-6 cm. fer^ad; rays very showy, golden yellow; 

 involucre hemispheric, its outer bracts linear-oblong or spatulate, equalling or 

 exceeding the broader, ovate or oblong, membranous inner ones; rays 8-IO, oval to 

 oblong, obtuse; achenes cuneate, truncate, 2 mm. long, retrorsely hispid on the 

 margins; pappus of 2-5 (usually 2), rigid downwardly barbed awns. In swamps 

 and wet meadows, Mass, to N. Car. and western N. Y. Aug. -Oct. 



2. Bidens ele^ans Greene. NARROW-RAYED BUR-MARIGOLD. Glabrous; 

 stem slender, sparingly branched, terete, red -purple. Leaves narrowly lanceo- 

 late, 6-8 cm. long, with few short salient teeth ; heads nodding, on long slender 

 peduncles; outer bracts of the involucre shorter than the inner; rays 68, about 3 

 times as long as the involucre; outer achenes 4-awned, the inner 3-awned; awns 

 and margins of the achenes retrorsely barbed. Southeastern Va. 



3. Bidens cernua L. SMALLER OR NODDING BUR-MARIGOLD. (I. F. 

 f. 3939.) Annual; stems glabrous, or hispid, usually erect, branched, 5-9 dm. high. 

 Leaves sessile and commonly somewhat connate-perfoliate at the base, glabrous, 

 acuminate, 7-15 cm. long, 6-25 mm. wide; heads numerous, globose, short-pedun- 

 cled, 1-2.5 cm - broad, nodding after or during flowering; rays 6-10, short (6-12 

 mm.), or none; involucre depressed-hemispheric, its outer bracts commonly ciliate, 

 often large, foliaceous and much exceeding the broad, yellowish-margined mem- 

 branous inner ones; achenes cuneate, about 4 mm. long, retrorsely hispid on the 

 margins; pappus of 2-4 (usually 4) downwardly barbed awns. In wet soil, N. S. 

 to Hudson Bay and Br. Col., south to N. Car., Mo. and Cal. Also in Europe and 

 Asia. July-Oct. It has recently been proposed by Professor E. L. Greene to 

 separate this into several species, and Mr. Wiegand has suggested two subspecies. 



4. Bidens connata Muhl. PURPLE-STEMMED SWAMP BEGGAR-TICKS. (I. F. 

 f. 3940.) Annual; glabrous throughout; stem erect, usually much branched, 1.5- 

 25 dm. high. Leaves petioled, thin, apex acuminate, base tapering, blade 5-12 cm. 

 long, 6-25 mm. wide, decurrent on the petiole, the lower sometimes with a pair of 

 lateral basal lobes; heads several or numerous, peduncled, 1-4 cm. broad; involu- 

 cre campanulate or hemispheric, its outer bracts ciliate or naked, somewhat exceed- 

 ing the ovate-oblong inner ones; rays none, or 15 and inconspicuous; stamens 

 often exserted; achenes cuneate or obovate, hairy and tubercled, or nearly glabrous, 

 often keeled, the margins with either erect or retrorse hairs, or both; pappus-awns 

 3 or 4; corolla 5 -toothed. In swamps or moist soil, N. S. to the N. W. Terr., south 

 to Del., Ga., Ky. and Mo. Aug. -Oct. 



Bidens connata pinnata S. Wats. Leaves pinnately divided into 4-6 pairs of acute, 

 entire to incised segments. Minn. 



5. Bidens comosa (A. Gray) Wiegand. LEAFY-BRACTED TICKSEED. (I. F. 

 f. 3941. ) Annual, glabrous; stem erect, branched, 1.5-10 dm. high. Leaves short- 

 petioled, with mostly smaller teeth than in B. connata, tapering to each end, the 

 petioles broadly margined ; heads several or numerous, I cm. broad or more ; outer 

 bracts of the involucre spatulate or lanceolate, foliaceous, often toothed, 2-4 times 

 as long as the head; corollas mostly 4-lobed, stamens and style included ; achenes 

 larger, 7-11 mm. long, evenly cuneate, very flat, retrorsely hairy; pappus-awns 

 commonly 3, downwardly barbed. In wet soil, southern N. Y. and Mass, to 111. 

 Aug.-Oct. 



6. Bidens acuta (Wiegand) Britton. PRAIRIE BEGGAR-TICKS. Similar to 

 B. comosa. Leaves lanceolate to oblong-lanceolate, sessile by a narrowed base, 

 4-8 cm. long, sharply serrate, the margins sparingly ciliate ; involucre broader 

 than high, 1.5-3 cm - broad; outer bracts foliaceous, ciliate, acutish, longer than 

 the achenes, spreading; inner bracts narrowly triangular-lanceolate, acute; achenes 

 cuneate, sparingly retrorsely hairy; awns 3, retrorsely barbed, the longer more 

 than half as long as the achene. In wet soil, Kans. and Mo. Aug.-Sept. [B. 

 comosa acuta Wiegand ; B. riparia Greene. ] 



7. Bidens bidentoides (Nutt.) Britton. SWAMP BEGGAR - TICKS. (I. F. 

 f. 3942.) Closely resembles B. connata, glabrous throughout; stem branched. 3-12 

 dm. high. Leaves petioled, or the upper sessile and entire, acuminate at the apex, 

 narrowed at the base; involucre narrowly or becoming somewhat broadly campan- 

 ulate, its outer bracts linear, foliaceous, not ciliate, usually much exceeding the 

 Oblong inner ones; rays none, or rarely present and veiy short; achenes linear- 



