9. Leaves bome on evident sometimes winged petioles up to 3 cm. long; achene 



body 4-8 mm. long, often tuberculate 7. B. tripartita. 



10(8). Outer phyllaries 3 to 5 (commonly 4), not manifestly ciliate; pappus awns 

 erect-hispid or smooth 8. B. discoidea. 



10. Outer phyllaries 5 to 8, regularly and copiously ciliate; pappus avms retror- 



sely barbed 9. B. frondosa. 



11(7). Achenes 5 to 9 (rarely 13) 10. B. leptocephala. 



11. Achenes 14 to 50 (12) 



12(11). Leaves all pinnately 3- or 5-parted with lance-oblong to rhombic-ovate 

 serrate to incised divisions 11. B. pilosa. 



12. Leaves all once or twice pinnately dissected (13) 



13(12). Outer and inner phyllaries more or less densely pilose or hirsute; leaves 

 2 or 3 times dissected into linear lobes 12. B. tenuisecta. 



13. Outer and inner phyllaries glabrous or merely short-ciliate, rarely sparsely 



pilose (14) 



14(13). Achenes dimorphic, a few peripheral ones clavate with a body only 4-7 

 mm. long; body of inner achenes 8-13 mm. long after anthesis; 

 awns 2, sometimes 3 13. B. Bigelovii. 



14. Achenes nearly all alike, the body often longer than 12 mm.; awns 3 or A.... 



14. B. bipinnata. 



1. Bidens laevis (L.) B.S.P. Fig. 767. 



Annual or perennial herb, erect or procumbent at base, 3-10 dm. tall; leaves 

 sessile, undivided, linear-lanceolate to lanceolate or rarely ovate-lanceolate, nar- 

 rowed at each end or at the base sometimes broad and connate, apically often 

 acuminate, regularly serrate with the teeth often slender and almost subulate, 

 glabrate or on the margin often sparsely ciliate, 5-15 cm. long; heads commonly 

 few, 3-7 cm. broad, 8-11 mm. high; involucre commonly hispid at base; outer 

 phyllaries 6 to 8, scarcely foliaceous, linear-lanceolate, apically obtuse or acute, 

 marginally subsparsely aciculate-ciliate, very rarely longer than the head; ray 

 flowers rarely absent, usually 7 or 8; rays golden-yellow, 15-30 mm. long, 

 obovate-lanceolate, apically rounded and often minutely 2- or 3-denticulate; 

 achenes narrowly cuneate, flat or 3- or 4-angulate, on the angles retrorsely barbed, 

 the body 6-9 mm. long; pappus awns 2 to 4, 3-5 mm. long, retrorsely barbed. 

 B. Nashii Small. 



Scattered near and in water of sloughs, lakes and streams, in marshes, irriga- 

 tion ditches and wet meadowlands, in Okla. {Waterfall) and in e., s.e., n.-cen. 

 Tex. and Edwards Plateau, rare in the Trans-Pecos, N.M. (San Juan and Taos 

 COS.) and Ariz. (Apache, Navajo, Yavapai and Santa Cruz cos.), summer; most 

 of U.S. except higher mt. areas. 



2. Bidens aurea (Ait.) Sherff. 



Erect perennial herb but often flowering first season, with tetragonous simply 

 branched stems to 1 m. tall; herbage glabrous or sometimes pubescent on young 

 growth; leaves thin, linear to lanceolate or elliptic-oblong, 0.5-1.2 cm. wide, to 

 10 cm. long, sharply serrate-dentate, undivided or less commonly lower ones 3- to 

 5-parted, with petioles to 4 cm. long; heads radiate, 2-5 cm. broad, about 1 cm. 

 high; outer involucral bracts 8 to 17, linear, acute and somewhat indurated at 

 apex, hispid-ciliate on margins but glabrous on face, 3-6 mm. long, 1 mm. wide 

 or less; inner bracts thinner, slightly wider but about as long; ray flowers 5 or 6, 

 yellow; ligules 10-30 mm. long, conspicuous, obovate; achenes linear-cuneate, 

 slightly quadrangular in cross section, black or dark gray, often more or less 

 papillose toward base, body 4-7 mm. long, tipped with 2 yellowish retrorsely 

 barbed awns 1.5-2.7 mm. long. 



1664 



