Genus 67.] 



THISTLE FAMILY. 



437 



2. Bidens cernua L. Smaller or Nod- 

 ding Bur-Marigold. (Fig. 3939.) 



Bidens cernua L. Sp. PI. 832. 1753. 

 Coreopsis Bidens L. loc. cit. 908. 1753. 



Annual; stems glabrous, or hispid, usually erect, 

 branched, ?/-l high. Leaves sessile and com- 

 monly somewhat connate-perfoliate .at the base, 

 lanceolate to oblong-lanceolate, usually coarsely 

 and sharply serrate, glabrous, acuminate, 3 / -6 / 

 long, jl'-i' wide; heads numerous, globose, short- 

 peduncled, / I - 2 / -i / broad, nodding after or during 

 flowering; rays 6-10, short (3 // -6 // ) l or none; in- 

 volucre depressed-hemispheric, its outer bracts 

 commonly ciliate, often large, foliaceous and 

 much exceeding the broad, yellowish-margined 

 membranous inner ones; achenes cuneate, about 

 7." long, retrorsely hispid on the margins; pappus 

 of 2-4 (usually 4), downwardly barbed awns. 



In wet soil, Nova Scotia to Hudson Bay and British 

 Columbia, south to Virginia, Missouri and California. 

 Also in Europe and Asia. Called also Water Agri- 

 mony, Double-tooth. July-Oct. 



Bidens connata Muhl. Purple-stemmed Swamp Beggar-ticks. (Fig. 3940.) 



B. connaia Muhl.; Willd. Sp. PL 3: 1718. l8o 4- 



Annual; glabrous throughout; stem erect, 

 usually much branched, 6'-8 high, purple. 

 Leaves petioled, lanceolate or oblong-lanceo- 

 late, sharply and coarsely serrate, apex acumi- 

 nate, base tapering, thin, 2 / ~5 / long, X'-i' wide, 

 .the uppermost sometimes sessile, nearly entire 

 and acutish, the lower sometimes with a pair of 

 lateral basal lobes, decurrent on the petiole; 

 heads several or numerous, peduncled, Yz'-'i.' 1 /^ 

 broad; involucre campanulate or hemispheric, 

 its outer bracts ciliate or naked, somewhat ex- 

 ceeding the ovate-oblong, inner ones; rays none, 

 or 1-5 and inconspicuous; disk-flowers orange; 

 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, the 2-4 pappus-awns 

 downwardly barbed. 



In swamps or moist soil, Nova Scotia to the North- 

 west Territory, south to Delaware, Georgia. Ken- 

 tucky and Missouri. Called also Cuckold, Harvest 

 Lice. Aug.-Oct. 



4. Bidens comosa (A. Gray) Wiegand. 

 Leafy-bracted Tickseed. (Fig. 3941.) 



B. connata var. comosa A. Gray, Man. Ed. 5, 261. 1867. 

 B. comosa Wiegand, Bull. Torr. Club, 24: 436. 1897. 



Annual, glabrous; stem erect, branched, 6'-4^ 

 high, straw-colored. Leaves short-petioled, lanceo- 

 late, coarsely serrate with mostly smaller teeth than 

 in B. connata, tapering to each end, the petioles 

 broadly margined; heads several or numerous, y z f 

 broad, or more; outer bracts of the involucre spatu- 

 late or lanceolate, foliaceous, often toothed, 2-4 

 times as long as the head; corollas mostly 4-lobed, 

 pale greenish yellow; stamens and style included; 

 achenes larger, y/% ,f -^Yz ,f long, evenly cuneate, 

 very flat, retrorsely hairy; pappus-awns commonly 

 3, downwardly barbed. 



In wet soil, southern New York and Massachusetts 

 to Illinois. Leaves thicker and paler than in B. con- 

 nata. Aug.-Oct. 



