GENUS 71. THISTLE FAMILY. 495 
1. Bidens laévis (L.) B.S.P. Larger or Smooth Bur-Marigold. Brook Sun- 
flower. Fig. 4505. 
Helianthus laevis L. Sp. Pl. 906. 1753. 
Bidens chrysanthemoides Michx. Fl. Bor. Am. 2: 
136. 1803. ; 
Bidens laevis B.S.P. Prel. Cat. N. Y. 29. 1888. 
Bidens lugens Greene, Pittonia 4: 254. 1901. 
Annual; glabrous throughout; stems branch- 
ed, erect or ascending, 1°-3° high. Leaves 
sessile, lanceolate, evenly serrate or serrulate, 
acuminate at the apex, narrowed to the some- 
times connate-perfoliate base, 3-8’ long, 3/-1’ 
wide; heads numerous, short-peduncled, erect 
in flower, often declined in fruit, 1-23’ broad; 
rays very showy, golden yellow; involucre 
hemispheric, its outer bracts linear-oblong or 
spatulate, equalling or exceeding the broader, 
ovate or oblong, membranous inner ones, 
shorter than the rays; rays 8-10, obovate- 
oblong, obtuse; achenes cuneate, truncate, 2’— 
4” long, retrorsely hispid on the margins; . 
pappus of 2-4 (usually 2), rigid downwardly 3 
barbed awns, shorter than the achene. i) 
In swamps and wet meadows, Massachusetts to Illinois, Kansas, Florida, Louisiana and Mexico. 
Northern records of this species apply to Bidens cernua. Aug.—Nov. 
Bidens élegans Greene, of southeastern Virginia, appears to be a narrow-rayed race of this 
species. 
2. Bidens cérnua L. Smaller or Nodding Bur-Marigold. Fig. 4506. 
Bidens cernua L. Sp. Pl. 832. 1753. 
Coreopsis Bidens L. loc. cit. 908. 1753. 
Annual; stems glabrous, or hispid, usually erect, 
branched, 3’-3° high. Leaves sessile and commonly 
somewhat connate-perfoliate at the base, lanceolate 
to oblong-lanceolate, usually coarsely and sharply 
serrate, glabrous, acuminate, 3’-6’ long, 2’-1’ wide; 
heads numerous, globose, short-peduncled, 47-1’ 
broad, nodding after or during flowering; rays 
6-10, short (3”-6”), or none; involucre depressed- 
hemispheric, its outer bracts commonly ciliate, 
often large, foliaceous and much exceeding the 
broad, yellowish-margined membranous inner ones + 
achenes cuneate, 2” long, retrorsely hispid on the 
margins; pappus of 2-4 (usually 4), downwardly 
barbed awns, about half as long as the achene. 
In wet soil, Nova Scotia to Hudson Bay and British 
Columbia, North Carolina, Missouri and California. 
Also in Europe and Asia. Consists of many races, 
differingin size. Water-agrimony. Double-tooth. Pitch- 
forks. July—Oct. 
Bidens Eatoni Fernald, known only from brackish soil, along the Merrimac River, Mass., has 
narrower heads and smaller achenes with awns either upwardly or downwardly barbed. 
A plant, with all the leaves pinnately divided, growing in the vicinity of Minneapolis, Minn., 
described as Bidens connata pinnata S. Wats., may be a hybrid with B. aristosa. 
