Ambrosia artemisiifolia var. paniculata (Michx.) Blank.

Ambrosia glandulosa Scheele, Linnaea 22: 157. 1849
Ambrosia coronopifolia var. [gracilis, &c] A. Gray, Bost. Jour. Nat. Hist. 6: 227. 1850. Ambrosia artemisiifolia paniculata Blankinship, Rep. Mo. Bot. Gard. 18: 173, mainly. 1907.
An annual herb, with branched root; stem 5-10 dm. high, terete with scattered appressed hairs: leaves pinnatifid or bipinnatifid, strigulose on both sides; petioles 2-3 cm. long; blades ovate in outline, 5-10 cm. long; divisions linear-lanceolate, acute or attenuate; staminate heads numerous, in racemes terminating the branches; involucre saucer-shaped or slightly broadly obconic, hispidulous, crenate, 3 mm. broad; paleae of the receptacle filiform; corolla puberulent; pistillate heads few in small clusters in the upper axils; body of the fruit broadly obovoid, scarcely 2 mm. long, glandular-granuliferous when young, in age glabrous and smooth; beak less than 0.5 mm. long.
Type locality: River bottom of the Cibolo, 15 miles west of New Braunsfels, Texas.
Distribution: Western Florida to Texas.

Ambrosia monophylla (Walt.) Rydberg
Iva monophylla Walt. Fl. Carol. 232. 1788.
Ambrosia paniculata Michx. Fl. Bor. Am. 2: 183. 1803.
Ambrosia artemisiifolia elatior Desc. Fl. Ant. 1: 239. 1821.
Ambrosia artemisiifolia 5 T. & G. Fl. N. Am. 2: 291. 1842.
Ambrosia artemisiifolia jamaicensis Griseb. Fl. Brit. W. Ind. 370. 1861.
Ambrosia artemisiifolia paniculata Blankinship, Rep. Mo. Bot. Gard. 18: 173. 1907.
An annual herb, with branched tap-root; stem 3-12 dm. high, hirsutulous and with scattered long hairs, obtusely angled, somewhat glandular-granuliferous, branched; lower leaves opposite, the upper alternate; petioles 2-3 cm. long, more or less hiruste; blades bipinnatifid to near the midrib, or the upper pinnate or entire, scabrous-puberulent above, strigose beneath; segments lanceolate, acute, more or less lobed or toothed; staminate heads numerous, in elongate racemes; peduncles 1-1.5 mm. long; involucre oblique, broadly obconic, 3 mm. broad, hispidulous, crenate on the margins; paleae of the receptacle filiform; pistillate heads in small clusters in the upper axils; body of the fruit fully 2 mm. long, broadly obovate, angled and rugose, glandular-granuliferous; spines 5-7, short, conic; beak 0.5 mm. long or less.
Type locality: Carolina.
Distribution: North Carolina to Mississippi, Texas, and Florida; Bahamas; Cuba; Jamaica; Santo Domingo (?).