Ordeb 10.— COMPOSITE 453 



branching plant, I to 2f high, with a panicle of large, showy, yellow heads. Lvs. 

 mostly opposite, thin, the upper 3-cleft, subsessile. Ach. £' long, awns half as 

 long. JL, Aug. 

 21 C. discoidea Torr. & Gr. Glabrous, much branched, erect ; lvs. ternate, loug- 

 petiolate ; lfts. ovate-lanceolate, strongly dentate, hds. discoid on slender pedun- 

 cles; outer involucre 3 — 5 linear-spatulate, leaf-like bracts; ach. linear-obloEg, 

 twice longer than the 2 erect awns which are hispid upwards. — d> Ohio to La. 

 Stem and branches purplish. Terminal leaflets 3 — 5 by \ — \\', lateral much 

 smaller. Heads small (3'' diam.), about 30-flowered. JX— Sept. 



58. BI V DENS, L. Burr-Marigold. (Lat. bidens, two-toothed; the 

 achcnia have two (or more) barbed teeth.) Involucre double ; scales 

 somewhat similar, or the outer foliaceous ; rays 4 to 8 (sometimes 

 none), neutral; disk-flowers perfect; receptacle chaffy, flat; pappus of 

 2 to 4 awns rough backwards ; achcnia obcomprcsseol, obscurely quad- 

 rangular. — Lvs. opposite, incised. Fls. yellow. 



§ Achcnia linear, somewhat 4-angleil, 3 to 4-awned. Rays few or none No. 1 



8 Achcnia flattened, broadest at top,— Rays none or very few Nos. 2 — 4 



— Rays about 8, showy, regular Nos. 5, 6 



1 B. bipinnata L. Spanish Needles. Smooth, lvs. bipinnate, lfts. lanceo- 

 late, pinnatitid, rays very short or none ; outer invol. the length of the inner ; 

 ach. slender, elongated. — (J) Grows in waste places N. T. (Sartwell), Ct. (Robbins). 

 St 2 to 4f high, branching, smooth. Lvs. bipinnately dissected, nearly smooth. 

 Hds. of flowers on long peduncles, each with 3 or 4 (or none) obscure, obovate, 

 yellow rays. Jl. — Sept. 



2 B. frondosa L. Hds. discoid ; outer invol. 6 times as long as the flower, 

 its leaflets ciliate at base ; lower lvs. pinnate, upper ones ternate, lanceolate, ser- 

 rate; ach. 2-awned. — (£ A common weed, in moist, cultivated fields throughout 

 Can. and U. S., often called Beggar-ticks from the 2-hornod achcnia which adhero 

 to every passer-by. St. 2f high, diffusely branched. Lower lvs. in 2s or 5h. 

 Fls. in clusters at tho end of the branches, without rays, yellow, leafy. Aug., 

 Sept 



3 B. comiata "Willd. nds. discoid, smooth; lvs. lanceolate, serrate, slightly 

 connate at base, lower ones mostly trifid ; outer scales longer than the head, leafy ; 

 ach. with 3 awns. — (1) In swamps and ditches, Can. N". Eng., to Mo. St. 1 to 3f 

 high, smooth and 4-furrowod, with opposite branches. Lvs. thin, taper-pointed, 

 often all undivided. Hds. scarcely ever with a ray. Aug. (B. tripartita, Bw.) 



4 B. cemua L. Hds. subradiate, cernuous ; outer invol. as long as the flower ; lvs. 

 all simple, lanceolate, subeonnate, dentate. — In swamps and ditches, Can. to Pa. 

 and Wise. St. 1 to 2f high, purplish, branched, round at base, striate above. 

 Branches opposite. Lvs. opposite, somewhat connate at base. Fls. yellowish 

 green, finally drooping, generally with small yellow rays about 8 in number. 

 Aug., Oct. 



5 B. chrysantliemoides L. Rays 3 times as long as tho nearly equal invol. ; 

 lvs. oblong, attenuate at each end, connate at base, dentate. — ;T) A low plant, with 

 large, yellow-rayed flowers, in muddy places, Can. and U. S. Stem 6 — 20' higb, 

 round and smooth. Leaves smooth, with few remote teeth, narrow, opposite, 

 with narrow, connate bases. Flowers commonly erect, rays about 8, largo, 

 spreading. Scarcely distinct from B. cernua. Sept., Oct. 



6 B. Beckii Torr. St. subsimple; submersed lvs. capillaceous-muliifld ; emersed 

 ones lanceolate, connate, acutely serrate or lanciniate ; fls. radiate ; rays longer 

 than tho involucre. — Zf In water, N. T. (Sartwell), Ac. Vt. (Chandler), N. to 

 Can. Stem 2 — 3f long, simple or with minute, slender branches above. Lower 



• leaves dissected as in Ranunculus aquatilis; upper 1 — 2' long, -£ as wide, deeply 

 serrate. Head solitary, terminal, yellow. July, Aug. 



59. ACMEL'LA, L. (Gr. dicftrj, a point; from the sharp taste of 

 the foliage?) Heads radiate; involucre shorter than the disk, double, 

 appressed, pubescent; receptacle, conical, chaffy; pales embracing the 

 ilowers; rays about 12, § , disk # ; achenia compressed, those of the 



