284 COMPOSITE, (composite family.) 



16. C. involucrata, Nutt. Heads rather larger, the outer scales 12-20, 

 mostly exceeding the inner, slender and hispid ; achenes with 2 short acute 

 teeth. — W. 111. to Kan. and Tex. 



H- -1- Rays none, or rarely rudimentary ; outer scales usually 3-5, loose, leafy, 

 commonly surpassing i/te short-pedunculate heads ; achenes narrowly cune- 

 ate ; plants glahrous, 1-3° high ; leaves petiolate. 



17. C. bidentoides, Nutt. Paniculately branched; leaves undivided, 

 lanceolate, coarsely toothed, tapering at both ends; heads 6- 10" long; achenes 

 nearly subulate, bearing a pair of very slender upwardly roughened awns sur- 

 passing the corolla (4" long), but shorter than the achene, often also 2 minute 

 teeth alternate with the awns. — Shores of Delaware River, near Philad., and 

 Delaware Bay, to ]\Id. Hybridizes with Bidens frondosa. 



18. C. discoidea, Torr. & Gray. Diffusely branched, 1-2° high ; leaves 

 ternately divided, slender-petioled ; leaflets ovate-lanceolate, pointed, coarsely 

 serrate ; heads 2 - 3" long ; achenes linear-wedge-shaped (2 - 3" lorg), bearing 

 a pair of short and stout upwardly-barbed awns of the length of the corolla. — 

 Wet banks and swamps. Conn, to Ohio, 111., and southward. July. 



56. BIDENS, L. . Bur-Marigold. 



Heads many-flowered ; the rays when present 3-8, neutral. Involucre double, 

 the outer commonly large and foliaceous. Receptacle flattish; the chaff decidu- 

 ous with the fruit. Achenes flattered parallel with the scales of the involucre, 

 or slender and 4 sided, crowned with 2 or more rigid and persistent awns which 

 are downwardly barbed. — Annual or perennial herbs, with opposite various 

 leaves, and mostly yellow flowers. (Latin, bidens, two-toothed.) 



* Achenes flat, not tapering at the summit; outer involucre foliaceous ; annuals. 

 1- Heads erect, nearly rayless; leaves mostly petiolate. 



1. B. frondosa, L. (Common Beggar-ticks. Stick-tight.) Smooth 

 or rather hairy, tall (2-6° high), branching; leaves 3 - d-dwided ; leofleta 

 mosdy stalked, lanceolate, pointed, coarsely toothed; outer involucre much 

 longer than the head, ciliate below ; achenes wedge-obovate, 2-awned, ciiiate (thfe 

 bristles ascending except near the summit). — Moist waste places; a coarse 

 troublesome Aveed, the achenes, as in the other species, adhering to clothing, 

 etc., by their retrorsely barbed awns. Hybrids occur with Coreopsis aristosa 

 and other species. July -Oct. 



2. B. COnnata, Muhl. (Swamp Beggar-ticks.) Smooth ( 1-2° high) ; 

 leaves lanceolate or oblong-lanceolate, pointed, sharply serrate, tapering into 

 margined slightly united petioles ; the lower often 3-divided, their lateral divi- 

 sions united at the base and decurrent on the petiole; outer scales longer than 

 the head, few, mostly obtuse; rays none; achenes narrowly wedge-form, 3- (2- 

 4-) aivned, the margins minutely retrorsely ciliate. — E. New Eng. to Minn., ann 

 southward. — Var. com6sa, Gray, is stouter, the leaves commonly all simple, 

 upper ones nearly sessile, the heads larger and with very leafy involucre. 111., 

 Ky., and westward. Aug. - Oct. — Var. pinxXta, Watson ; leaves nearly all 

 pinnatelv divided, the 5-7 narrow divisions sparingly incised ; achenes 4-awned. 

 Hennepin Co., Minn. [F. L. Couillard). 



