Order 70.— COMPOSITE, 443 



Bf high. Radical petioles If long. Lvs. 4 to 12' long, J aa wido. Hda. white, 

 with 5 very short cueullate rays. Jl. — Sept. 

 2 P. HysterophOTUs L. Annual, puberulent, decuvibent, lower las. bipinnatifid, 

 upper linear ; hds. numerous, very small, in a diffage panicle. — River banlts, Fla. 

 to la. 



44. rVA, L. Mahsh Elder. Hiohwater Shrub. Heads dia- 

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

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

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

 opposite. 



1 I. frutesoens L. Shrubby; lvs. fleshy, lanceolato, coarsely serrate; upper 

 lance-linear, entire ; hda. 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 lvs. Hds. small, green, drooping on short stalks, in leafy, 

 paniculate racemes. Jl. — Sept. 



2 I. cilidta Willd. Amvaal, hairy; lvs. ovate, acumhiate, petiolato, coarsely 

 tootlied, upper lance-ovata; hds. spicaie; scales 3, distinct, roundish, ciliaie; ach. 

 3. — Wet grounds, IlL to La. A coarse plant of no beauty, 3 to li high. Lvs. 

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

 Ambrosia. Aiig. — Oct. . 



3 I. imbriodria Walt. Herbaceous, terete, glabrous; lvs. fleshy, linear-lanceo- 

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

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

 y 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. Hobse-wekd. (Gr. af^ppoaia, food of the 

 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 lvs. 

 and unsightly flowers. 



S sterile heads sessile, densely splcnte, chaff/. Leaves alternate No. 4 



§ Sterile beads pedicellate, raccmed, not chaffy. — Leaves opposite No. 1 



— Leaves alternate Nos. 2, 8 



1 A. trifida L. Hairj-, rough; lvs. S-lobed, serrate, the lobes oval-lanceolate, 

 acuminate ; fr. with 6 ribs ending below the conical summit. — (D A very tall, 

 herbaceous plant, along streams, &c. Can. and TJ. 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 eaten 

 by horses. 



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

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



2 A. artemisiaefdlia L. Hoq-weed. Lvs. tiaice-pinnatifid, nearly smooth; petioles 

 ciliate; rac. terminal, panicled; st. virgate. — (T) A common and troublesome 

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

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

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

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

 Sept. (A. elatior Ph.) 



3 A. psylostachya DC. Whitish with appressed woolly hairs, branched ; lvs. 

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

 natifid ; sterile hds. In spieate racemes, fertile clustered at the base of the sterile 

 spikes, in the axils of the upper leaves ; fr. hairy.— .(^ Prairies, Wis. to Tex 

 Stem 1 — 6f high, at length very branching and leafy. Aug., Sept. 



