138 GAMOPETALOUS EXOGENS 



hastate-lobed, the lower ones pinnatifid ; rays small, trifid, whitish 

 or ochroleucous. 

 CANADIAN POLYMNIA. 



Stem 2 to 4 or 5 feet high, branching. Leaves 4 to 8 or 10 inches long, and 8 to 6 

 inches broad, very thin, mostly 3-lobed and rather dilated towards the apex, 

 deeply hastate-lobed at base, often alternate, the lower ones deeply pinnatifid, 

 with clasping stipule-like appendages at the base of the petiole. Heads of flowers 

 small, loosely paniculate; rays scarcely 1 third of an inch tong. Akenes dark 

 brown, with a prominent rib on each margin, and one on the inner face ; crowned 

 with a whitish protuberant ring. 

 Hob. Moist, rich woods : rare. Fl. Aug. Fr. Sept. 



Obs. This species, formerly indigenous along the Brandywine, is 

 now extremely rare, except in the gardens of the curious. The 

 recent plant has a considerable odor, something between that of 

 Yarrow and Tansey. 



2. 1". Uvedaliifcj L. Roughish-pubescent; leaves broad-ovate, 

 sinuate-lobed, the lower ones sub-palmate; rays elongated, 3- 

 toothed, deep yellow. 

 UVEDAL'S POLYMNIA. 



Stem 3 or 4 to 6 or 8 feet high, stouter than the preceding, often with opposite 

 axillary branches above. Leaves 4 to 10 or 12 inches long, thin, ciliate, the 

 lower ones nearly as wide as long, 3- to 5-lobed, abruptly contracted at base to a 

 tapering winged petiole which is somewhat sinuate-lobed, and 2 to 4 inches in 

 length, Heads of flowers larger than in the preceding, paniculate ; rays about 

 an inch long, 

 Hob. Great Valley; near Brooke's Mill: rare. Fl. Aug. Fr. Sept. 



199. AMBROSIA, Tournef. 



[Poetically, Food of the Gods; a name singularly inappropriate tt> our plant.] 

 Heads monoicous, the staminate ones 5- to 20-flowered, in terminal 

 racemes, the pistillate 1-flowered, in bracteate clusters of 2 or 3 

 to 5, sessile at the base of the racemes, or in the axils of the upper 

 leaves. Involucre of the staminate heads flattish ; scales several, 

 united into a cup ; florets all funnel-form. Involucre of the pistillate 

 florets turbinate, closely embracing the akene, like a utricle, acumi- 

 nate, with 4 to 8 (usually 5 or 6) pointed tubercles near the sum- 

 mit. Corolla none. Akene obovoid. Chiefly annuals : leaves 

 opposite and alternate, petiolate, lobed or pinnatifidly dissected. 



1. A. trifiila, L. Stem tall and stout, rough-hairy; leaves pal- 

 mately 3- to 5-lobed, lobes oval-lanceolate. 

 TRIFID AMBROSIA. 



Stem 3 to 6 or 8 feet high, angular, branched. Leaves 4 to 6 or 8 inches long, 

 usually 3-lobed (sometimes undivided), opposite, hairy and scabrous, on slightly 

 margined ciliate petioles about an inch in length. Staminate heads numerous, in 

 long terminal paniculate racemes ; florets whitish. Involucre of the pistillate florets 

 strongly 5- or 6-ribbed, the ribs with as many acute points at top. 

 Hob. Low grounds; waste places, &c. : frequent. Fl. Aug. Fr. Octo. 



Obs. A coarse homely weed, and frequent enough, but not so 

 abundant as the following species. If the generic name has refer- 

 ence to the mythological Ambrosia, it must be something like Lucus, 

 a non lucendo ! I should have supposed it more likely to have been 



