3. Ophioglossum engelmannii Prantl, Ber. Deutsch. Bot. Ges. 1: 351. 1883.
Roots to 25 per plant, tan to brown, 0.5-1.5mm diam., straight, producing proliferations. Stem upright, to 1.5 cm, 4 mm diam., leaves 1-2 per stem. Trophophore stalk to 0.1 cm, 0.01 times length of blade. Trophophore blade erect to spreading, commonly ± folded when alive, uniformly pale green throughout when dried, dull, ovate to ovate-lanceolate, 10 × 4.5 cm, firm, herbaceous, base narrowed abruptly, apex with apiculum to 0.8 mm; venation complex-reticulate, veinlets forming numerous, very tiny, secondary areoles within the major areoles. Sporophores arising at ground level, 1.3-2.5 times as long as trophophore; sporangial clusters 2-4 × 0.13-0.31 cm, pairs of sporangia 20-40, apiculum 0-1.3 mm.
Leaves appearing early-late spring, often with second flush later in season following summer rains. Mostly in soil over limestone in open fields, pastures, and cedar glades; 50-1000 m; Ala., Ariz., Ark., Fla., Ga., Ill., Ind., Kans., Ky., La., Miss., Mo., Ohio, Okla., N.Mex., N.C., Tenn., Tex., Va., W.Va.; Mexico; Central America.