107. Euphorbia longicruris Scheele, Linnaea. 22: 152. 1849.
Wedge-leaf spurge Wedge-leaf spurge
Tithymalus longicruris (Scheele) Small
Herbs, annual, with taproot. Stems erect, usually unbranched, occasionally branched later in season, 5–25 cm, glabrous. Leaves: petiole 0–0.5 mm; blade cuneate-spatulate to obovate, 5–15 × 2–6 mm, base broadly attenuate, margins entire, apex rounded to obtuse, mucronate, surfaces glabrous; venation pinnate, midvein prominent. Cyathial arrangement: terminal pleiochasial branches 3, each many times 2-branched; pleiochasial bracts obovate, similar in size to distal leaves; dichasial bracts basally subconnate, strongly imbricate and often obscuring internodes, reniform to semiorbiculate, base cordate, margins entire, apex rounded; axillary cymose branches 0–5. Cyathia: peduncle 0.3–0.5 mm. Involucre campanulate, 1.5–2 × 1–1.5 mm, glabrous; glands 4, crescent-shaped to elliptic, 0.4–0.8 × 0.8–1.1 mm; horns divergent, 0.5–0.8 mm. Staminate flowers 10–15. Pistillate flowers: ovary glabrous; styles 0.5–0.6 mm, 2-fid. Capsules ovoid-globose, 2–2.8 × 2.5–3 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 1.6–2.1 mm. Seeds gray to purple-gray or sometimes nearly black, oblong, 1.3–1.6 × 0.9–1.2 mm, strongly small-pitted; caruncle umbonate, depressed-conic, 0.5 × 0.7 mm.
Flowering and fruiting spring. Grasslands, open prairies, sites with rocky, usually calcareous soils; 300–800 m; Ark., Kans., Okla., Tex.
Euphorbia longicruris is quite similar to the other small, annual members of subg. Esula in the south-central United States and can best be distinguished from those species by its imbricate dichasial bracts that form little tufts of overlapping leaves at the ends of the pleiochasial branches.