CosMiDiuM. COMPOSIT.E. 351 



scales of the inner involucre united above the middle, obtuse, without scari- 

 ous margins, the exterior ovate, obtuse, very short ; rays none ; ovaries 

 oblong-linear, crowned with 2 subulate retrorsely pectinate-hispid (decidu- 

 ous?) awns. — Bidens gracilis, Torr. ! in ann.lyc. Neiv York, 2. p. 215. 



Upper Arkansas, on the Canadian River, JJr. James ! — 11 Stems 2 feet 

 high, branched from the base, dichoiomous and naked at the summit, striate. 

 Chaff &c. as in tlie preceding. Awns stout, concave, about the length of 

 the tube of the corolla. — The single specimen brought by Dr. James, the 

 only one extant, is not very perfect. Perhaps it sometimes bears ray- 

 flowers. 



104. BIDENS. Linn.; Gcertn.fr. t. 167; DC. prodr. 5. p. 593. 



Heads many-flowered ; the ray-flowers (3-8) neutral, often inconspicuous 

 or wanting ; those of the disk tubular, perfect. Involucre double; the scales 

 dissimilar or nearly similar, the exterior frequently large and foUaceous. 

 Receptacle flattish; the chaff deciduous with the fruit. Corolla with a slen- 

 der tube, and an infundibuliform-campanulate 5-toothed limb. Branches of 

 the style hairy at the summit, terminated by an acute or subulate cone. 

 Achenia obcompressed, or slender and more or less 4-sided, often attenuate 

 or rostrate at the summit, crowned with 2-4 (rarely 5-6) rigid and persistent 

 retrorsely barbed or hispid awns. — Annual or sometimes perennial (mostly 

 American) herbs; with opposite, incised, serrate, or divided leaves, feather- 

 veined (the numerous primary veins often running to the sinuses) and reti- 

 culated. Flowers mostly yellow or yellowish : the anthers pale or brownish- 



§ 1. Achenia flat, oval or cuneiform, not attenuated at the sunmiit ; the 

 margins usually ciliate or hispid mostly in a downward direction.^ 

 Plattcarp^a, DC. 



1. B. frondosa (hinn.) : glabrous or slightly hairy ; lower leaves pinnate- 

 ly 5-, the upper commonly 3-divided ; the divisions distinct and mostly pe- 

 tiolulate, lanceolate, or the terminal one ovate-lanceolate, acuminate, coarsely 

 serrate (rarely 3-lobed or parted); heads discoid, pedicellate; scales of the 

 exterior foliaceous involucre longer than the head, mostly acute, conspicuous- 

 ly ciliate towards the base ; achenia obovate-cuneiform, 2-awned, pubescent 

 and ciliate with chieflv erect hairs. — Linn.! spec. {ed. 2) 2. p. 1166; 

 Michx. ! fl. 2. p. 136 ; Willd. ! spec. 3. p. 1718 ; Pursh, I. c. ; Ell. sk. 2. p. 

 431 ; Hook. fl. Bor.-Am. 1. p. 314; Bigel. fl. Bosl. ed. 2. p. 294 ; Dar- 

 lingt. ! fl. Cest. p. 486 ; DC. ! I. c. 



JVloist fertile soil, throughout Canada! and the United States! abounding 

 around barn-yards and moist corn-fields, where it is a very troublesome 

 weed. July-Sept. — Stem 2-6 feet high, branched. Petioles, and often the 

 lower surface of the leaves, a little hairy. Scales of ihe outer involucre 8-12, 

 varying from twice to six limes the length of the disk ; the inner ovate-lan- 

 ceolate, brownish. Flowers greenish-yellow. Margins of the achenia up- 

 wardly ciliate, except near the summit, where the bristles are usually re- 

 trorse. — Stick- tight. Burr-Marigold. 



2. B. connata (Muhl.) : glabrous ; leaves lanceolate or oblong-lanceolate, 

 acute or acuminate, sharply serrate, tapering into margined petioles, slightly 

 connate at the base ; the lower ones often ternately divided ; the lateral seg- 



