29. Bidens Le. Sticktight, 
Annuel herbs with opposite, simple or pinnate leaves. Heads either 
with or without ray-flowers, their involucres consisting of two dissimilar 
series, the outer herbaceous, oblong or oblanceolate, the inner shorter, 
broader, chaffy, firm, brownish, passing into the similar oblanceolate 
or lanceolate deciduous bracts of the discs; receptacles naked at maturity, 
convex, Ray flowers yellow when present, sterile; disc-flowers yellow, 
Achenes strongly flattened, cuneiform, bearing a rib on each face and 
either 2 or 4 rigid spinose retrorsely barbed ayms, 
Oo Ray flowers usually present; leaves simple /, Be. cernua 
o Ray flowers absent; leaves 3-5=pinnate 2. 8B. vulgata 
1. B. cernua L. ~~ 7 A weedy herb of great variability in aspect and 
stature, the stems 50-80 cm, tall, branching in the inflorescence, the 
branches ascending or arcuate, glaucous, sometimes sparingly pubescent 
above; leaves simple, 5-12 cm, long, the lowermost oblanceolate, soon 
deciduous, the upper oblong-oblanceolete or narrowly elliptical, acute or 
acuminate, sessile, sharply serrate, glabrous; outer bracts of the involucre 
12-20 mn, long, oblong-elliptical, mostly narrowed at the base with an 
obtuse or rounded sinus, the inner 7-9 mm. long, ovate; ray-corollas 
present, bright yellow, 12-15 mm, long; disc-corollas yellow,3 mm, long; 
body of the achenes narrowly cuneiform, 7-8 mn, long, bearing 4 spinose 
avns 3-5.5 mn. long, retrorsely barbed, as are also the ribs and the margins, 
Frequent in stagnant water or boggy ground at low elevations, 
oti 
