CAEDUACEAE 1281 



7. Bidens discoidea (T. & G. ) Britton. Stem slender, diffusely branched, nearly or 

 quite glabrous, 3-15 dm. high : leaf-blades 3-divided, the segments lanceolate or ovate- 

 lanceolate, 4-9 cm. long, sharply and coarsely serrate below the entire long-acuminate 

 tip : heads very small and numerous, 8-10 mm. broad : outer bracts of the involucre 

 mostly 4, spatulate-linear, rarely exceeding the disk, glabrous : rays none : disk-corollas 

 orange, 5-lobed : achenes small, 4-5.5 mm. long, black, cuneate, thickisji, tuberculate or 

 nearly smooth, hairy, the margins and the 2 short awns erect-barbed. [Coreopsis discoidea 



In swamps, Massachusetts to Michigan, North Carolina and Texas. Late summer and fall. 



8. Bidens cernua L. Stem low, pale green, 2-7 dm. high, nearly glabrous, the 

 branches very short, decreasing down the stem : leaf-blades undivided, 6-16 cm. long, 

 lanceolate or linear-lanceolate, more or less connate by the broad bases, acuminate, serrate, 

 with coarse distant teeth : heads very large, broader than high, nodding in fruit : outer 

 bracts of the involucre 7-8, unequal, exceeding the disk and spreading : rays usually pres- 

 ent, bright yellow, the ligules about one-half longer than the disk, the ovaries glabrous 

 except the margin, and awnless : disk-corollas orange, 5-lobed : achenes narrowly cuneate, 

 slightly dilated at the summit, 4-angled, the margins retrorsely barbed and tuberculate, 

 the awns 4, slender, retrorsely barbed. 



In swamps, Nova Scotia to North Carolina, Missouri and Oregon. Also in Europe and Asia. 

 Summer and fall. 



9. Bidens laevis (L.) B.S.P. Stem glabrous, 5-10 mm. high, the branches all 

 toward the summit of the stem, slender, ascending : leaf-blades undivided, 7-13 cm. long, 

 elliptic-lanceolate, serrate with small inconspicuous teeth, acute, contracted toward the 

 sessile base : heads medium, nearly globular, erect or nodding in fruit : outer bracts of the 

 involucre 7-8, rarely longer than the disk : rays very large, the ligules 2-3 cm. long, 

 golden yellow, the ovaries as in the last : disk-corollas orange, 5-lobed : achenes cuneate, 

 neither dilated nor contracted at the top, not tuberculate, the margins and 24 awns 

 retrorsely barbed. [B. chrysanthemoides Michx.] 



In swamps, mainly near the coast, Massachusetts to Georgia. Summer and fall. 



10. Bidens Nashii Small. Similar to the next preceding species but slightly suc- 

 culent, less branched : leaves ascending ; blades broader and thicker, oblong-lanceolate or 

 oblanceolate, with very broad but scarcely connate bases, finely serrate or entire : achenes 

 slightly contracted at the summit. 



In swamps, Florida to Texas. Summer and fall. 



11. Bidens aristosa (Michx.) Britton. Annual or biennial, 'much branched, 3-10 

 dm. high : leaf-blades pinnately 5-7 -divided, the segments lanceolate, acuminate, serrate, 

 incised or pinnatifid, slightly pubescent beneath : heads numerous, 2-5 cm. broad : outer 

 bracts of the involucre 8-10, linear-spatulate, rarely ciliate, not surpassing the inner : rays 

 6-10, the ligules golden yellow, the ovaries ciliate and awnless : achenes obovoid, flat, 

 strigose and hispid-ciliate ; awns 2, slender, as long as the achene-body or shorter, the 

 barbs erect or reflexed. [Coreopsis aristosa Michx.] 



In swamps, Illinois to Kansas, Arkansas and Texas. Summer and fall. B. aristosa mtitica (A. 

 Gray) Wiegand. A form with pappus-awns wanting. Mississippi and Louisiana. 



12. Bidens involucrata (Nutt. ) Britton. Annual or biennial, much branched, 

 3-10 dm. high, minutely pubescent ; leaf-blades pinnately divided, the segments narrow, 

 linear-lanceolate, incised or pinnatifid, long-acuminate : heads 3-5 cm. broad : outer 

 bracts of the involucre 12-20, linear, acutish, hispid on back and margins, mostly surpass- 

 ing the inner : rays several, the ligules golden yellow, the ovaries awnless, ciliate through- 

 out : disk-corollas 5-lobed : stamens exserted : achenes very flat, obovoid, slightly contracted 

 at the top, strigose-ciliate, bidentulate. [Coreopsis involucrata Nutt.] 



In swamps, Illinois to Kansas, Arkansas and Texas. Also in Delaware. Summer and fall. 



13. Bidens trichospdrma (Michx.) Britton. Annual or biennial, tall and glabrous, 

 much branched, 6-15 dm. high : leaf -blades pinnately divided, with 4-8 narrowly lanceo- 

 late, serrate or incised, acute or acuminate segments : heads 4-6 cm. broad : outer bracts 

 of the involucre linear-spatulate, rarely ciliate, equalling the disk: rays several, the 

 ligules bright yellow, 12-25 mm. long, the ovaries bidentulate at the summit : disk-corollas 

 deep yellow, 5-lobed : stamens exserted : achenes narrowly cuneate, slightly strigose- 

 ciliate above ; awns 2, about equalling the breadth of the achene, erect-barbed. [Coreopsis, 

 trichosperma Michx.] 



In swamps, Masachusetts to Illinois, Kentucky and Georgia. Summer and fall. 



14. Bidens coronata (L.) Fisch. Annual, glabrous or nearly so, branched, 3-10 

 dm. high : leaf-blades 7-12 cm. long, 3-5-divided or rarely mostly simple, the segments 

 lanceolate, acuminate, serrate, the lateral much smaller : heads 2-5 cm. broad : outer bracts 



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