COMPOSITE. (COMPOSITE FAMILY.) 2G1 



42. 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 chair decidu- 

 ous with the fruit. Achenia flattened 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.) 



* Achenia flat, not tapering at the summit. (All annuals?) 



1. B. frondbsa, L. (Common Beggar-ticks.) Smooth or rather hairy, 

 tall (2° -6° high) and branching; leaves 3 - 5-divided ; the leaflets mostly stalked, 

 lanceolate, pointed, coarsely toothed; outer leafy involucre much longer than 

 the head, eiliate helow ; rays none or few and very small ; achenia wedge-obovate, 

 2-awned, the margins eiliate with upwardly-turned bristles, except near the summit. 

 — Moist waste places : a coarse troublesome weed, the achenia, as in the other 

 species, adhering by their retrorsely barbed awns to the dress, and to the fleece 

 of animals. July - Oct. 



2. B. connata, Muhl. (Swamp Beggar-ticks.) Smooth (l°-2° high) ; 

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

 gined petioles which are slightly united at the base ; the lower often 3-divided, their 

 lateral divisions united at tlie base and decurrent on the petiole; scales of the outer 

 involucre longer than the head, few, mostly obtuse; rags none; achenia narrowly 

 wedge-form, 3- (2-4-) owned, the margins minutely retrorsely eiliate. (B. tripartita, 

 Digel.) — A thin-leaved more petioled form is B. petiolata, Nutt. — E. New Eng- 

 land to Illinois, and southward. — Var. com6sa is stouter, the leaves commonly 

 all simple, upper ones nearly sessile, the heads larger and with more numerous 

 and leafy bracts. — Illinois, Kentucky, and westward. Aug. -Oct. 



3. B. eernua, L. (Smaller Bcr-Marigold.) Nearly smooth (5'- 10' 

 high); leaves all undivided, lanceolate, unequally serrate, scarcely connate; heads 

 nodding, with or without (light yellow) rays: outer involucre longer than the 

 head ; achenia wedge-obovate, 4-awned, the margins downwardly barbed. — 

 Wet places, Virginia to Wisconsin, and northward. July - Sept. — Rays, when 

 present, smaller than in the next, the leaves irregularly toothed, and the outer 

 involucre more leaf-like. (Eu.) 



4. B. chrysanthemoides, Michx. (Larger Bcr-Marigold.) Smooth, 

 erect, or reclining at the base (6' -30' high) ; leaves lanceolate, tapering at both 

 ends, more or less connate, regularly serrate ; outer involucre mostly shorter than 

 the showy golden-yellow (V long) rays; ..achenia wedge-shaped, with almost prickly 

 downwardly barbed margins ; awns 2, 3, or 4. — Swamps : common. Aug. - 

 Oct. — Northward it runs into No. 3. 



* * Achenia linear or awl-shaped, 4-sided, slender, tapering at the summit. 



5. B. Beckii, Torr. (Water Marigold.) Aquatic, perhaps perennial 

 smooth ; stems long and slender, bearing crowded immersed leaves many times dis- 

 sected into fine capillary divisions; the few emerging leaves lanceolate, slightly 

 connate, toothed ; heads single, short-peduncled ; involucre much shorter than the 

 showy (golden yellow) rays ; achenia linear, thickish, smooth (^' long), bearing 4 - 

 6 stout divergent awns which are an inch lonjr and barbed onlv towards the 



