

ORDER LXVIH. COMPOSITE. 383 



3. B. subacau'lis, (Nutt.) Minutely strigose, pubescent at first 

 Leaves radical, deeply sinuate, bipinnatifid, often lyrate, somewhat peti- 

 oled ; scapes bearing a single head. Torr. & Gray. 



Genus XXXVIL— PARTHE'NIUM. L. 

 (From partlienos, a virgin.) 



Involucre 5-leaved, villous. Ray florets small, pistillate, those 

 of the disk staminate. Receptacle flat, chaffy. Seed obovate. 

 Pappus none. 



1. P. integrifo'lium, (L.) Stem erect, slightly scabrous, striate. 

 Leaves alternate, ovate-lanceolate, unequally toothed, sessile, scabrous, 

 the upper ones amplexicaul. Flowers in terminal corymbs ; ray florets 

 5, small, the exterior chaff, broad. — White or yellowish. If. June — 

 Sept. Upper and middle Car. and Geo. 1 — 2 feet. 



2. P. hysteropho'rus, (L.) Stem hirsute, diffusely branched or de- 

 cumbent. Leaves bipinnatifid, the uppermost linear, undivided. Heads 

 small, paniculate. — Florida. 



Genus XXXVIII— I'VA. L. 



(Origin of the name unknown.) 



Involucre 5 — 10-leaved. Ray florets pistillate, those of the 

 disk staminate. Anthers not united. Receptacle bristly. Seed 

 obovate. Pappus none. 



1. I. frutes'cens, (L.) A shrub, with numerous opposite branches, 

 slightly furrowed, somewhat scabrous and pubescent when young. 

 Leaves opposite, lanceolate, attenuate at the base, deeply serrate, sca- 

 brous, of a greenish hue. Flowers axillary, forming terminal panicles ; 

 involucre viscidly pubescent, 5-leaved, leaves nearly round. Ray fo- 

 rets 5, those of the disk 6 — 7. — Pale purple. ^. July — Sept. On the 

 seacoast. 3— 8 feet. Marsh Elder. 



2. I. imbrica'ta, (Walt.) Stem herbaceous, terete, slightly angled to- 

 ward the summit, glabrous, becoming purple. Leaves sessile, linear- 

 lanceolate, cun.-ute, succulent, the upper ones usually alternate and 

 entire, the lower frequently opposite and toothed. Flowers axillary, 

 pendulous; involucre with 6 — 9 fleshy leaves, with the margins lacer- 

 ate. Ray floret* 2, those of the disk numerous. — White. If. July — 

 Oct. On the seacoast. 



Genus XXXIX.— AMBROSIA. Tourn. 

 (From ambrosia, food of the gods.) 



Flowers numerous, staminate florets with the involucre hem- 

 ispherical, 1 -leaved, many-flowered. Anthers approximate, but 

 not united. Receptacle naked, pistillate florets, with the invo- 

 lucre 1-leaved, entire, or 5-toothed, 1 -flowered. Corolla none. 

 Styles 2. Fruit a nut formed from the indurated calyx, 1 -seeded. 



1. A tpif'ida, (L.) Stem erect, rough, hirsute. Leaves usually op- 

 posite, 3-lobed, serrate, the lobes oval-lanceolate, acuminate, hairy, ser- 

 rate. Flowers in small axillary and terminal npikes, forming a large 



