ORDER 10. COMPOSITES. 453 



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

 mostly opposite, thin, the upper 3-cleft, eubsessile. Ach. j' long, awns half aj 

 long. JL, Aug. 



21 C. discoidea Torr. & Gr. Glabrous, much branched, erect ; Ivs. ternate, long- 

 petiolate ; Ifts. ovate-lanceolate, strongly dentate, Ms. discoid on slender pedun- 

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

 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. JL Sept. 



58. BI'DENS, L. BURR-MARIGOLD, (Lat. bidens, two-toothed ; the 

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

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

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

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

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



Aeheni.i linear, somewhat 4-nngled, 3 to 4-awned. Rays few or none No. 1 



Achenia flattened, broadest at fop, Rays none or vc'ry few Nos. 24 



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



1 B. bipinnata L. SPANISH NEEDLES. Smooth, Ivs. bipinnate, Ills, lanceo- 

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

 ach. slender, elongated. Grows in waste places Conn., N. T., west to I1L 

 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. Eds. discoid ; outer invol. C times as long as the flower, 

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

 rate; ach. 1-awned. CD A common weed, in moist, cultivated fields throughout 

 Can. and U. S., often called Beggar-ticks from the 2-horned achenia which adhere 

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

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

 Sept. 



3 B. connata Willd. lids, discoid, smooth; Ivs. lanceolate, serrate, slightly 

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

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

 high, sraoolh and 4-furrowed, with opposite branches. Lvs. thin, taper-pointed, 

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



4 B. cernua L. lids, subradiate, cernuou-s } outer invol. as long as the flower Ivs. 

 aU simple, lanceolate, subconnate, 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 yeJlow rays about 8 in number. 

 Aug., Oct. 



5 B. chrysanthemoides L. Rays 3 times as long as the nearly equal invol. ; 

 Ivs. oblong, attenuate at each end, connate at base, dentate. fj) A low plant, with 

 large, yellow-rayed flowers, in muddy places, Can. and U. S. fctem 6 20' high, 

 round a:id smooth. Leaves smooth, with few remote teeth, narrow, opposite, 

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

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



6 B. Beckii Torr. St. subsimple; submersed Ivs. capillaceous-multijid ; emersed 

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

 than the involucre. 1[ In water, N. Y. (Sartwell), &c. 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. tkp/, a point; from the sharp taste of 

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

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

 ilowers; rays about 12, $, disk $ 5 achenia compressed, those of tho 



