1. Ophioglossum californicum Prantl, Ber. Deutsch. Bot. Ges. 1: 355. 1883.
Ophioglossum lusitanicum Linnaeus subsp. californicum (Prantl) R. T. Clausen
Roots to 16 per plant, pale brown, 0.5-1 mm diam., producing proliferations. Stem upright, to 1.6 cm, 5mm diam., commonly 2 leaves per stem. Trophophore stalk 0-1.8cm, to 2.5 times length of trophophore blade. Trophophore blade erect to spreading, commonly ± folded when alive, green, dull, without pale central band when dried, to 4.3 × 1 cm (rarely 0.4 × 0.3 mm), herbaceous, thick, gradually tapering to base, apex attenuate; venation complex-reticulate, with numerous parallel narrow areoles, each with 1-several included veinlets. Sporophores arising near ground level, 1-2.5 times length of trophophore; sporangial clusters 8-15 × 1-3 mm, with 8-15 pairs of sporangia, apiculum 0.3-1 mm.
Leaves appearing in late winter and early spring; apparently absent during dry years. Open grassy fields and prairies; 50-300 m; Calif.; Mexico.
Ophioglossum californicum differs from the Old World species O . lusitanicum in that O . lusitanicum has a narrowly linear to linear-oblanceolate trophophore that is 1/4 to 1/2 as wide as long; O . lusitanicum also has a much simpler venation and usually lacks an apiculum.