7. Ophioglossum vulgatum Linnaeus, Sp. Pl. 2: 1062. 1753.
Southern adder's-tongue, herbe sans couture
Ophioglossum pycnostichum (Fernald) A.Löve & D.Löve; O. vulgatum var. pycnostichum Fernald
Roots to 20 per plant, 0.3-0.9 mm diam., producing proliferations. Stem upright, to 1 cm, 3 mm diam., leaves 1 per stem. Trophophore stalk formed abruptly at base, to 5mm, sometimes more, 0.05 times length of trophophore blade. Trophophore blade erect to spreading, usually plane when alive, dark green, somewhat shiny, mostly ovate to ovate-trowel-shaped, widest in proximal half, to 10 × 4cm, firm, herbaceous, base tapering abruptly, apex rounded; venation complex-reticulate with included free veinlets in areoles. Sporophores arising at ground level, stalk 2-4 times length of trophophore; sporangial clusters 20-40 × 1-4 mm, with 10-35 pairs of sporangia, apiculum 1-1.5mm. 2 n =ca.1320.
Leaves appearing spring-early summer. Shaded secondary woods, rich wooded slopes, forested bottomlands, and floodplain woods, south of Wisconsin glaciation; 0-800m; Ala., Ariz., Ark., Del., Fla., Ga., Ill., Ind., Ky., La., Mich., Miss., Mo., N.J., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va.; Mexico; Eurasia.
In addition to characteristics given in the key, Ophioglossum vulgatum differs from O . pusillum in having an unusually persistent leathery basal leaf sheath (B.W. McAlpin 1971; W.H. Wagner Jr. 1971b) rather than an ephemeral one and in having smaller spores (mostly 35-45µm in O . vulgatum compared with 50-60 µm in O . pusillum ). The chromosome number of O . vulgatum in India and Europe has been reported as 2 n =480, and that may be the number of most North America populations, which are small spored. In the Appalachians, however, a distinctive large-spored form has a chromosome number of 2 n =ca. 1320.