OKDER 70. COMPOSITE. 443 



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

 with 5 very short cucullate rays. Jl. Sept. 



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

 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 chaffy ; 

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

 opposite. 



1 I. frutescens 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; ach. 

 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. i^nbricaria Walt. Herbaceous, terete, glabrous; Ivs. fleshy, linear-lanceo- 

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

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

 It 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. AMBRCTSIA, Tourn. HORSE-WEED. (Gr. dufipooia, 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 Ivs. 

 and unsightly flowers. 



Sterile heads sessile, densely spicate. chaffy. Leaves alternate Xo. 4 



Sterile heads pedicellate, racerned, not chaffy. Leaves opposite No. 1 



Leaves alternate Nos. 2, 3 



1 A. trifida L. Hairy, rough; Ivs. 3-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 U. S., common. Stem 5 101* 

 high, erect, branching, farrowed. 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. 



* <3. INTEGRIFOLIA. Lvs. ovate, acuminate, serrate, bristly on both sides, ciliate 

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



2 A. artemisiaefolia L. HOG- WEED. Lvs. twice-pinnatifid, nearly smooth ; petioles 

 ciliate; rac. terminal, panicled; st. virgate. CD 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, branching, pubescent when young. 

 Leaves with segments acute and parallel, barren flowers small, green, hi 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 oppressed woolly hairs, branched ; Ivs. 

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

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

 spikes, in the axils of the upper leaves ; Jr. hairy. (I) Prairies, Wis. to Tex. 

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



