Forked spurge (Euphorbia bifurcata)

Description

Euphorbia bifurcata Engelmann in W. H. Emory, Rep. U.S. Mex. Bound. 1859. Herbs, annual, with slender, fibrous taproot. Stems erect, 20-70 cm, glabrous or with few scattered spreading hairs; branches arcuate, branching appearing dichotomous. Leaves usually alternate, occasionally opposite at proximalmost node; petiole 15-49 mm, glabrous; blade usually ovate, rarely oblong or elliptic, 13-54 - 7-38 mm, base usually rounded to broadly cuneate, rarely truncate, margins finely serrulate, apex obtuse, surfaces glabrous or with few scattered hairs; venation pinnate, midvein prominent. Cyathial arrangement: terminal dichasial branches 2, few-branched (weakly defined); pleiochasial bracts 2-3, opposite or whorled, wholly green, similar in shape and size to distal leaves; dichasial bracts smaller than distal leaves, often white at base. Cyathia: peduncle 0.9-3.5(-6.2) mm. Involucre tubular or obconic, 1-1.7 - 0.7-1.4 mm, glabrous except for few hairs on lobes; involucral lobes divided into several linear, smooth lobes, glands, greenish, sessile and broadly attached, 0.3-0.4 - 0.4-0.8 mm, opening oblong to subcircular, glabrous; appendages petaloid, white, elliptic, oblong, transversely oblong, or forming thin, lunate rim on gland margin, not incurved and covering glands, 0.3-0.9 - 0.6-1.3 mm, entire, undulate or slightly lobed, glabrous. Staminate flowers 20-30. Pistillate flowers: ovary glabrous; styles 0.6-1 mm, 2-fid 1/2 length. Capsules oblate, 2.8-3.1 - 3.6-4.5 mm, glabrous; columella 1.9-2.4 mm. Seeds brown to blackish, ovoid, rounded in cross section, 1.9-2.4 - 1.5-1.8 mm, irregularly and coarsely tuberculate; caruncle absent or rudimentary. Flowering and fruiting summer-fall. Riparian areas with cottonwoods and willows, pinyon pine woodlands, pine-oak forests, Douglas fir forests with pines; 1900-2300 m; N.Mex., Tex.; Mexico; Central America (Guatemala). Euphorbia bifurcata is found in the mountains of southern New Mexico (Do-a Ana, Grant, Lincoln, Otero, and Sierra counties) and trans-Pecos Texas (Brewster, Jeff Davis, and Presidio counties).