6. Bidens polylepis Blake. 



Annual or biennial herb, glabrous, 3-10 dm. tall; leaves petiolate (petioles 

 to 25 mm. long), including the petiole 8-15 cm. long, commonly bipinnate; leaf- 

 lets lanceolate or linear-lanceolate, acuminate, sharply serrate, membranous, ciliate; 

 heads 2-5 cm. broad, 7-9 mm. high; outer phyllaries numerous, commonly 15 to 

 20, usually spreading or reflexed, linear-elongate, conspicuously hispid-ciliate, 

 dorsally hispid or glabrate, 10-27 mm. long; inner phyllaries lanceolate, shorter; 

 rays about 8, golden-yellow, 10-25 mm. long, oblong-oblanceolate, apically entire 

 or obscurely denticulate; achenes flat, brown or blackish-brown, 5.5-7.5 mm. 

 long; pappus awns nearly obsolete or slightly developed and with erect-hispid 

 teeth. 



In wet prairies, low meadows, low swampy woods, borders of oxbow lakes, in 

 river floodplain and upland ponds, waste ground, sandy flats at edge of lakes in 

 Okla. (Creek, Pittsburg, Pushmataha, McCurtain, LeFlore and Ottawa cos.) and 

 e. and s.e. Tex., spring-early summer; midwest U.S. and s. to Tex. 



7. Bidens tripartita L. 



Annual, nearly or quite glabrous, 1-20 dm. tall; leaves simple, serrate, often 

 very sharply so, sometimes deeply tripartite, commonly 3-15 cm. long and 

 to 4 cm. wide, borne on evident sometimes winged petioles to about 3 cm. long; 

 heads erect, rayless or occasionally with rays to about 4 mm. long, broadly 

 campanulate to hemispheric, at least the terminal one generally more than 30- 

 flowered, the disk 8-20 mm. wide; outer phyllaries about 4 to 9, herbaceous, often 

 much-enlarged and leaflike; achenes cuneate or obovate-cuneate, flat or com- 

 pressed-quadrangular, commonly with a median rib on at least one face, glabrous 

 or somewhat short-hairy, brown or blackish to purplish, 4-8 mm. long, often 

 tuberculate; pappus of 2 to 4 awns. 



A cosmopolitan weed of wet waste places, in Okla. (Waterfall) and reported from 

 the Tex. Panhandle (Hemphill Co.), Aug.-Oct.; otherwise known from Eur. and 

 adv. in Que. and N.H. 



8. Bidens discoidea (T. & G.) Britt. Fig. 770. 



Annual herb, 3-18 dm. tall; leaves petiolate (petioles 1-4 cm. long), including 

 the petiole 5-12 cm. long, membranous, tripartite; leaflets lanceolate or ovate- 

 lanceolate, acuminate, serrate, all commonly petiolulate, sometimes obscurely 

 ciliate; heads numerous, the disk finally 7-9 mm. broad and 6-7 mm. high; 

 involucre glabrous; outer phyllaries 3 to 5 (usually 4), foliaceous, linear-spatulate, 

 membranous, not distinctly ciliate, commonly surpassing the disk, 7-25 mm. long; 

 inner phyllaries oblong-lanceolate, membranous, subequal to the disk; ray flowers 

 absent; achenes blackish, flattish, linear-cuneate, often tuberculate, pilose-hispid, 

 the body 3-6.2 mm. long; pappus awns 0.2-2.2 mm. long, erect, hispid. 



In swampy lowlands, alluvial bottomlands and sink-hole ponds, in Okla. (Mc- 

 Curtain Co.) and in e. and s.e. Tex., spring and early summer; Ala. to Tex., n. to 

 N.S., Me., Que., Ont., Mich., Wis. and Minn. 



9. Bidens frondosa L. Beggar-ticks, stick-tights. Fig. 77 1 . 



Annual herb, more or less glabrous, paniculate-branched, 5-12 dm. tall; leaves 

 petiolate (petioles 1-6 cm. long), including the petiole 5-15 (-20) cm. long, 

 pinnately 3- or 5-divided, membranous, ciliate, on the upper surface commonly 

 glabrate, on the lower surface glabrate or obscurely and sparsely or even rather 

 densely clothed with minute setae; leaflets lanceolate, acuminate, serrate, the 

 terminal one slenderly petiolulate; heads about 1 cm. broad, 6 mm. high; involucre 

 basally hispid; outer phyllaries 5 to 8 or occasionally as many as 10, conspicuously 

 ciliate, often very long (even 3-5 cm. long) and foliaceous, linear-spatulate; inner 



1668 



