ORDER 70. COMPOSITE. 443 



5f high. Radical petioles If long. Lvs. 4 to 12' long, A as wide. Hds. 

 with 5 very short cucullate rays. Jl. Sept. 

 2 P. Hysterophorus L. Annual, puberulent, decumbent, lower Ivs. bipinnatifid, 

 upper linear ; hds. numerous, very small, in a diffuse panicle. River banks, Fla. 

 to La. 



44. TVA, L. MARSH ELDER. HIGHWATER SHRUB. Heads dis- 

 coid, monoecious, involucre of 3 to 9 scales, distinct or partly united ; 

 marginal flowers 1 to 5, fertile, the others sterile ; receptacle chaft'y ; 

 achenia obconic, obtuse ; pappus none. Herbs or shrubs. Lower Ivs. 

 opposite. 



1 I. frutesceiis L. Shrubby; Ivs. fleshy, lanceolate, coarsely serrate; upper 

 lance-linear, entire; hds. axillary; scales 5, distinct, rounded; ach. 5. Borders 

 of salt marshes, Mass, to Fla., common. St. 3 to 8f high, with numerous op- 

 posite branches and Ivs. Hds. small, green, drooping on short stalks, in leafy, 

 paniculate racemes. Jl. Sept. 



2 I. ciliata "Willd. Annual, hairy; Ivs. ovate, acuminate, petiolate, coarsely 

 toothed, upper lance-ovate; hds. spicate; scales 3, distinct, roundish, ciliate; actt. 

 3. Wet grounds, 111. to La. A coarse plant of no beauty, 3 to 7f high. Lvs. 

 3 to 4' long. Spikes dense, 3 to 5' long, numerous, panicled, green, like an 

 Ambrosia. Aug. Oct. 



3 I. imbricaria "Walt. Herbaceous, terete, glabrous; Ivs. fleshy, linear-lanceo- 

 late, 3-nerved, tapering to the sessile base ; hds. axillary ; invol. of 6 to 9, fleshy, 

 obtuse, rounded scales in 2 rows, their margins scarious, lacerated ; ach. 2 to 4. 

 U Sea coast, N. Car. to Fla. Plant 1 to 2f high. Lvs. 1 to 2' long. Hds. 

 drooping, on short pedicels, in leafy clusters or racemes. Jl. Oct. 



45. AMBRO'SIA, Tourn. HORSE-WEED. (Gr. dfippoota, food of tho 

 gods; a term strangely applied). Hds. heterocephalous. Sterile: 

 involucre of several scales united into a depressed, hemispherical cup, 

 many-flowered: anthers approximate, but distinct; receptacle naked. 

 Fertile ; involucre 1-leaved, entire or 5-toothed, 1-flowered ; corolla 



; styles 2 ; stamens 0. Herbaceous plants with mostly opposite Ivs. 

 and unsightly flowers. 



Sterile heads sessile, densely spicate, chaffy. Leaves alternate , No. 4 



| Sterile heads pedicellate, racemed, not chaffy. Leaves opposite No. 1 



Leaves alternate Nos. 2, it 



1 A. trifida L. Hairy, rough; Ivs. 3-lobed, serrate, the lobes oval-lanceolato, 

 acuminate ; fr. with G ribs ending below the conical summit. 3) A very tall, 

 herbaceous plant, along streams, &c. Can. and U. S., common. Stem 5 lOf 

 high, erect, branching, furrowed. Leaves opposite, in 3 large, deep lobes, with 

 long points and close serratures. Flowers mean and obscure, in slender, leafless, 

 terminal racemes, the fertile in axillary glomerules. Aug. It is greedily eateu 

 by horses. 



(3. INTEGRIFOLIA. Lvs. ovate, acuminate, serrate, bristly on both sides, ciliato 

 at base, often some of them 3-lobed. (A. integrifolia Muhl.) 



2 A. artemisiasfolia L. HOG- WEED. Lvs. twice-pinnatijid, nearly smooth; petioles 

 ciliate ; rac. terminal, panicled ; st. virgate. X A. common and troublesomo 

 weed of the gardens, fields, &c. (Can. to Ga.) far more worthy of its English 

 than its Latin name. Stem 2 3f high, branching, pubescent when young. 

 Leaves with segments acute and parallel. Barren flowers small, green, in ter- 

 minal racemes, the fertile ones sessile about the axils of tho upper leaves. Aug., 

 Sept (A. elatior Ph.) 



3 A. psylostachya DC. Whitish with oppressed woolly hairs, branched ; Iva. 

 crowded, rigid, the lower opposite, bipinnatifid, upper lanceolate, sessile, pin- 

 natifid ; sterile hds. in spicate racemes, fertile clustered at the base of the sterila 

 spikes, in the axils of the upper leaves; fr. hairy. <l) Prairies, Wis. to Tex, 

 Stem 1 5f high, at length very branching and leafy. Aug., Sept. 



