Euphorbia longicruris

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.

Phenology: Flowering and fruiting spring.
Habitat: Grasslands, open prairies, sites with rocky, usually calcareous soils.
Elevation: 300–800 m.

Ark., Kans., Okla., Tex.

Discussion

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.

Selected References

None.

Lower Taxa