BiDENs. COMPOSITE. 387 



Annual. Stem 2-6 feet higli, often dark purple, branched, sparsely hairy. Leaves 

 pinnately divided, thin ; the lower ones usually with 5 divisions, the upper very generally 

 3-parted : divisions 2-4 inches long, rather coarsely and acutely serrate, attenuate at the 

 base into short stalks : common petiole 1-3 inches long. Heads never radiate. Scales of 

 the exterior involucre unequal and variable in length, sometimes spatulate and rather obtuse ; 

 inner scales ovate-lanceolate, scarious, brownish. Flowers greenish-yellow. Achenia ciliate 

 upward, except near the summit : awns longer than the somewhat persistent corolla. 



Moist fertile soils ; common in cultivated fields, etc. July - September. A troublesome 

 weed. The ripe achenia of this and other species adhere to the clothes, and to the coats of 

 animals, by their barbed awns. 



2. BiDENS coNNATA, Mulil. Sioamp Beggar-ticks. 



Leaves lanceolate or oblong-lanceolate, acute or acuminate, sharply serrate, tapering into 

 margined petioles, slightly connate at the base , the lower ones often ternatcly divided , the 

 lateral segments connate at the base and decurrent on the petiole ; heads discoid, mostly on 

 short peduncles, erect ; scales of the exterior involucre longer than the head, mostly obtuse, 

 scarcely ciliate ; achenia narrowly cuneiform, smooth, with the margin hispid downward, 

 2-4- (commonly 3-) awned. — Muhl. in Willd. sp. 3. p. 1718 ; Pursh, fl. 2. p. 566 ; Ell. 

 sk. 2. p. 430 ; Torr. compend. ;?. 312 ; Beck, hot. p. 207 ; Hook. Jl. Bor.-Am. 1. p. 314 ; 

 DC. prodr. 5. p. 594 ; Torr. <^ Gr. fl. N. Am. 2. p. 352. B. tripartita, Bigel. fl. Bost. 

 p. 294. B. petiolata, Nutt. in jour. acad. Phil. 7. p. 99 ; Darlingt. fl. Cest. p. 486. 



Annual. Stem 1-2 feet or more high, smooth, branching, purple. Leaves often all un- 

 divided, of a thin texture, acuminate at each end. Exterior involucre foliaceous, variable in 

 length, oflen more than twice as long as the disk. Corolla greenish-yellow ; the rays always 

 wanting. Awns stout, longer than the corolla. 



Low wet places ; common. August - September. 



3. BiDENs CERNUA, Linti. ' Swamp Beggar-ticks. 



Leaves all undivided, lanceolate, unequally serrate, the upper ones slightly connate ; heads 

 (discoid or radiate) on slender peduncles, often nodding ; exterior involucre longer than the 

 head; achenia obovate-cuneiform, 4-awned, the margin hispid downward. — Linn. sp. 2. 

 p. 832 ; Engl. hot. t. 1114; Pursh, fl. 2. p. 566 ; Torr. compend. p. 31 1 ; Bevk, hot. p. 207 ; 

 Hook. fl. Bor.-Am. 2. p. 314 ; DC. prodr. 5. p. 595 ; Torr. ^ Gr. fl. N. Am. 2. p. 352. 

 B. minima, Linn. Coreopsis Bidens, Linn, (the radiate form). 



Annual. Stem 6 inches to 2 feet high, smooth, or sometimes slightly hairy towards the 

 summit. Leaves 3-6 inches long, smooth, thin, coarsely serrate, attenuate at the base, 

 acuminate. Heads commonly discoid, but sometimes more or less radiate : peduncles 1-3 

 inches long. Scales of the exterior involucre foliaceous, oblanceolate, acute, often more than 



49* 



