Ophioglossum vulgatum f. pseudopodum Blake. (Rhodora 15: 87. 1913.) This is a form in which the sterile blade is narrowed below into a stalklike base a fourth to two thirds as long as the expanded portion. This form has been found in St. Joseph County by R. M. Tryon, Jr. P. E. I., Ont. to Alaska, southw. to Fla. and Mex.; also in Eurasia.
Roots yellow to tan, to 15 per plant, 0.3-1 mm diam., producing proliferations. Stem upright, to 2 cm, 3mm diam., 1 leaf per stem. Trophophore stalk expanding gradually into blade. Trophophore blade erect or spreading, usually plane when alive, pale green, dull, mostly oblanceolate to obovate to ovate, widest point in middle, to 10 × 3.5 cm, soft, herbaceous, base tapering gradually, apex rounded; venation complex-reticulate, with included free veinlets in areoles. Sporophores arising at ground level, 2.5-4.5 times length of trophophore; sporangial clusters 20-45 × 1-4 mm, with 10-40 pairs of sporangia, apiculum 1-2 mm. 2 n =960. Leaves appearing midspring. Frequent and widespread, open fens, marsh edges, pastures, and grassy shores and roadside ditches, north of the southern boundary of Wisconsin glaciation; 100-2000 m; B.C., N.B., N.S., Ont., Que.; Alaska, Calif., Conn., Idaho, Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Vt., Va., Wash., W.Va., Wis. Ophioglossum pusillum is inconspicuous and may be much more common than collections indicate. It differs from O . vulgatum in having an ephemeral, membranous basal sheath.
Perennial fern 8 - 25 cm tall Stem: single, upright, very short and inconspicuous (up to 2 cm tall and 3 mm diameter), and with a thickened base (caudex). Spores: thousands per sac, all of one kind, three-sectioned (trilete), thick-walled, and with a bumpy or pimply surface. The spores give rise to the gametophyte (the sexual phase of the plant), which is broadly egg-shaped, unbranched, tiny (0.2 - 2 cm tall, 1 - 3 mm diameter), fleshy, brown to white, underground, saprophytic, and inhabited by symbiotic fungi (mycorrhizae). Leaf: one per stem, arising directly from an expanded, clasping base, which forms a short-lived, membranous sheath around stem apex. The single leaf is made up of two parts arising from a shared stalk: a sterile, green, expanded blade portion (trophophore); and a fertile, narrow, spore-bearing portion (sporophore). Leaves appear in mid-spring. Roots: up to fifteen per plant, unbranched, yellow to tan, 0.3 - 1 mm in diameter, and smooth.
Similar species: Ophioglossum pusillum is the only species of this genus in the Chicago Region, but just to the southeast another similar species, O. vulgatum, occurs. These two species even used to be considered varieties of the same species. The more southeastern species differs by having dark green, somewhat shiny, firm leaf blades that are more egg- or trowel-shaped with an abruptly tapered base. That species also has different habitat requirements, preferring damp forests.
Habitat and ecology: Occasional in moist sedge prairies, fens, seeps, sedge meadows, and other open somewhat moist places.
Occurence in the Chicago region: native
Notes: At first glance this species, as many Ophioglossum species, is often confused for a seedling of a monocot flowering plant . For many years, this species was considered just a variety of O. vulgatum under the name O. vulgatum var. pseudopodum.