476 COMPOSITAE (COMPOSITE FAMILY) 
NODDING BUR MARIGOLD 
Bidens cérnua, L. 
Other English names: Double-tooth, Water Agrimony. 
Native. Annual. Propagates by seeds. 
Time of bloom: July to October. 
Seed-time: August to November. 
Range: Nova Scotia to British Columbia, southward to the Caro- 
linas, Missouri, and California; also in Europe and Asia. 
Habitat: Marshy meadows, swamps, and along streams. 
This species, usually in company with the similar, but larger, 
Brook SUNFLOWER (Bidens laévis, B.S.P.), often covers acres of 
lowlands with yellow bloom, to be suc- 
ceeded by the clutching brown fruits. It 
is small, six to thirty inches high, pale 
green, smooth, or sometimes slightly 
rough-hairy, rather stout, with short 
branches. Leaves opposite, narrowly 
lance-shaped, sessile, often joined at base, 
edged with coarse, distant, and unequal 
teeth. Heads numerous, large, broader 
than their height, the peduncles short and 
at first erect but drooping after fertiliza- 
tion; rays often lacking, but, when pres- 
ent, bright yellow, exceeding the length 
of the disk by about one-half; disk-florets 
orange-yellow, five-lobed; outer bracts of 
the involucre longer than the head, usually 
bristle-fringed and spreading; the inner 
row short, ovate, pointed, with yellowish, 
scarious margins. Achenes wedge-shaped, 
Fic. 330.—Nodding Bur dull brown, four-angled, four-awned, an- 
Marigold (Bidens cernua). gles and awns barbed downward, causing 
re these fruits to be even more readily at- 
tached to clothing and the coats of animals than those of the 
preceding species. (Fig. 330.) 
The same measures for suppression are necessary as for the 
Swamp Beggar-tick. 
