COMPOSITE. 185 



Old fields. Can. to Flor, Aug., Sept. Q—Stem 1—4 feet high, usually 

 rough. Heads small ; the sterile ones in long slender paniculate racemes. Fruit 

 solitary or in small clusters at the base of the sterile racemes, armed with about 

 6 short acute teeth. A troublesome weed. Hog-weed. 



4. A. pajiiculata Mich. : stem branching, paniculate at the summit, and 

 with the petioles villous ; leaves green on both sides, bi-pinnatifid, the seg- 

 ments lanceolate ; fruit somewhat clustered, small, obovate, slightly awned. 

 Iva monophyllu Wait. 



Old' fields. Can. to Flor. July— Sept. (T). Pursh.—Stem 2—4 feet bigh. 

 Heads in simple terminal and axillary racemes. Paniculate^ag-weed. 



5. A. heterophylla MuM. : stem pubescent or villous, paniculate; cauline 

 leaves pinnatifid, subdentate, petiolate ; those of the branches lanceolate, 

 sessile; petioles with long ciUae ; racemes terminal, solitary. A. Peruviana 

 Willd. 



Banks of streams. Penn. July — Sept. (1). Muhl. — Fruit with 5 — 6 acute 

 teeth below the summit. Perhaps this and the preceding are only varieties of 

 A. artimisicBfolia. Various-leaved Rag-weed. 



29. IVA. Linn.— Msixsh. Elder. 

 (Origin of the name doubtftil.> 



Heads monoecious/ not radiate. Fertile flowers 1 — 5, mar- 

 ginal, with a small tubular corolla. Sterile flowers numerous, 

 with a tubular -campanulate corolla. Scales of the involucre 

 3— 5 in a single series, or 6 — 9 and imbricated. ' Receptacle 

 small, chaffy. Achenia obovoid, somewhat compressed. Pap- 

 pus none. 



I. frutescens Linn. : shrubby, smooth ; leaves opposite, oval or oval-lan- 

 ceolate, somewhat petioled, deeply-serrate, slightly scabrous ; uppermost 

 linear-lanceolate, entire ; heads - axillary, depressed-globose, pedicellate ; 

 scales of the involucre 5, orbicular. 



Sea coast. Mass. to Flor. Aug., Sept. T-j. — Stem 3 — 8 feet high, much 

 branched. Leaves thick and somewhat fleshy. Heads numerous, small, green- 

 ish, in axillary leafy racemes, forming a large terminal panicle. 



Marsh Elder. Highwater Shrub. 



30. HELIOPSIS. Pcrs.— Ox-eye. 



(From the Greek ^Xtoj; the sun, and oipis, appearance; in allusion to the form 

 of the heads of flowers.) 



Heads many-flowered ; the ray flowers in one series, ligulate, 

 fertile ; those of the disk tubular, perfect. Involucre in 2 — 3 

 series ; the outer scales leafy, the rest imbricate. Receptacle 

 conic. Achenia angular, partly surrounded by the chaff". 



H. IcBvis Pers. : stem smooth ; leaves smoothish, ovate-lanceolate or ob- 

 long-ovate, tapering at base into a petiole, serrate, 3- nerved. Helianthui 

 Icevis Linn. 



Banks of streams Tliroughout the U. S. Aug., Sept. %.— Stem 2 — 4 feet 



