CARDUACEAE 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, thickish, tuberculate or 
n smooth, hairy, the margins and the 2 short awns erect-barbed. [Coreopsis discoidea 
,&G.] 
In swamps, Massachusetts to Michigan, North Carolina and Texas. Late summer and fall. 
8. Bidens cérnua 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 laévis (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 2-4 awns 
retrorsely barbed.  [ B. chrysanthemoides Michx.] 
In swamps, mainly near the coast, Massachusetts to Georgia. Summer and fall. 
10. Bidens Náshii 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. 
ll. Bidens aristósa (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 müfica (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 trichospérma (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 coronàta (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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