COMPOSITE. 209 



HAB. Penn. to Car. July. U.Stem 46 feet high. Flowers 

 in a loose terminal corymb ; rays 14, long, yellow. Mr. Elliott 

 doubts whether the two last species are sufficiently distinct. 



SUBORDER VII, AMBROSIACE^. 

 46. IVA. Unn. 



Involucre about 5-leaved or 5-parted. Florets of the ray 5, 

 naked. Receptacle bristly. Pappus none. Acines obovate. 

 {Anthers approximate, not united.) Syngenesia. Necessaria. 



I. frutesccns Linn. : shrubby ; leaves opposite, lanceolate, deeply ser- 

 rate, slightly scabrous ; heads globular-depressed. 



HAB. Sea coast. N. Y. to Flor. Aug. !. Shrub 38 feet 

 ,. . high, with numerous opposite branches and leaves. Flowers 

 small, in axillary leafy raceme, forming a large terminal pani- 

 cle. 



47. AMBROSIA. Linn. 



Monoecious. STERILE FL. Involucre 1-leaved, hemisphe- 

 rical, many-flowered. Anthers approximate but not 'united. 

 Receptacle naked. FERTILE FL. Involucre 1-leavcd, entire 

 or 5-toothed, 1-flowered. Carol none. Styles 2. Nut 

 formed from the indurated calyx, 1-seeded. 



Monoecia. Pentandria. 



1. A. integrifolia MM. : leaves ovate, sessile, acuminate, serrate, 

 hispid on both sides, ciliate at base ; racemes terminal and mostly ter- 



nate. ***' 



HAB. Near ponds and ditches. Penn. and Virg. July Sept. 

 0. Pursh. 



2. A. bidentata Mich. : very hairy ; leaves closely sessile, simple, 

 lanceolate. 1 2 toothed on each side near the base ; fruit 4-sided, 4- 

 spined below the summit. 



HAB. Allegany mountains. W. to Illinois. Perhaps not in the 

 limits assigned to the present work. July Sept. 0. 



3. Jj. trifida Linn. : hirsute, rough ; leaves 3-lobed, serrate ; the 

 lobes oval-lanceolate, acuminate ; fruit 6-spined below the summit. 



HAB. Banks of streams. N. Y. to Car. W. to Miss. July 

 Sept. 0. Stem 4 8 feet high. Leaves very large. Flowers 

 in large terminal panicles composed of long axillary and termi- 

 nal spikes. 



4. A. elatior Linn. : stem virgate ; f leaves bipinnatifid, nearly smooth; 

 petioles conspicuously ciliate ; racemes terminal. 



HAB. Old fields. Can. to Car. Aug., Sept. ^.Stem 14 

 (at the south 47) feet high. Flowers in paniculate racemes. 

 Nut with 6 spines. Hog Weed. 



n ^ H ' 18* 



