Thelypteris ovata R. P. St. John var. lindheimeri (C. Christens.) A. R. Smith, lindheimer’s maiden fern. Perennial herb, appearing evergreen, rhizomatous, fibrous–rooted, with several leaves emerging from ground, in range < 100 cm tall; shoot with leaves arising directly from rhizome 10—25 mm apart, leaves monomorphic, aboveground having short–pilose nonglandular hairs mostly 0.2—0.5 mm long and stalked glandular hairs to 0.15 mm long having yellow heads on axes and mostly restricted to lower surface of foliage, not viscid; rhizome shallow, horizontal, creeping, to 6 mm thick, covered with brown scales, having adventitious roots on lower side.
Leaves (fronds) alternate, odd–2–pinnately compound–lobed having primary leaflets (pinnae) paired and subopposite ca. 3/4 (12+ pairs), approaching end of rachis pinnae alternating and final portion pinnately lobed at tip, petiolate with petiole ≥ blade, without stipules; petiole ± cylindric at base (slightly flattened) to channeled from below midpoint, in range to 400 × 2.5+ mm, purple–red at base and light green above aging tannish, having a fine line on each lateral side, with scattered pilose and glandular hairs, having lanceolate to narrowly triangular papery brown (purplish) scales near rhizome, the scales to 1.5 mm long, with several short–pilose hairs on surface; blade triangular in outline, rachis channeled, light green aging tannish, with slender, colorless scales to 3 mm long, aging tannish and early–abscising, rachis having pairs of pinnae spaced 25—29 mm apart at base decreasing upward, pinnae < 10—110 × < 4—22 mm, essentially sessile, gradually shorter to tip (often with 20+ pinnae on each side of rachis), rachilla absent, pinnate lobes (pinnules) on large blades triangular–ovate, to 10 × 5 mm, the largest at base incrementally decreasing to tip, angled forward, sinuses nearly to whitish midvein (costus) and often puckered at sinuses, entire and margins somewhat inrolled, broadly acute to obtuse or rounded at tip, sometimes trailing basal pinnule of a pinnae having a sublobe adjacent to rachis, pinnately veined, the lateral veins to 14 and parallel, ending at margin (“sinus”), costus and whitish midvein of pinnules raised and channeled on upper surface and veins raised on lower surface, upper surface of blade mostly glabrous with some nonglandular and glandular hairs along costus and pinnule midvein of the lower pinnae, lower surface short–pilose and with stalked glandular hairs having yellow heads especially along veins and margins.
Sori on lower surface on lobes along lateral veins close to margins in 2 lines, the lines 1—6(—7), roughly round in outline, mostly 0.5—0.7 mm across, not touching adjacent sori, with ca. 20 sporangia; indusium attached in center and kidney–shaped concealing immature sporangia, greenish drying colorless, short–pilose and with shorter glandular hairs, including glandular–ciliate on lobe margins.
Sporangia ca. 0.2 mm across, dark red, lacking glandular hairs.
A. C. Gibson