Thelypteris dentata
Thelypteris palustris
downy maiden fern, downy shield fern, tapering tri-vein fern
eastern marsh fern, marsh fern, meadow fern, thélyptère des marais
short-creeping, 4–6 mm diam.
often somewhat dimorphic, evergreen, often closely placed, 50–150 cm, fertile leaves with longer petioles and more contracted pinnae.
often purplish brown, 15–50 cm × 3–6 mm, at base with brown, linear-lanceolate, hairy scales.
(25–)40–100 cm, 1–4(–6) proximal pairs of pinnae reduced, blade gradually tapered to pinnatifid apex.
7–17 × 1–3 cm, incised 1/2–3/4 of width;
segments rounded at apex, basal acroscopic segment of proximal pinnae often auriculate;
proximal pair of veins from adjacent segments united at obtuse angle below sinus with excurrent vein 2–4 mm.
round, medial to supramedial;
indusia tan, pubescent, hairs 0.1–0.3 mm;
sporangial stalks with orangish, stalked glands.
abaxially of uniformly short hairs 0.1–0.2 mm on costae, veins, and blade tissue;
veins adaxially with stouter hairs, also with hairs 0.1–0.2 mm on blade tissue.
= 144.
Thelypteris dentata
Thelypteris palustris
Thelypteris dentata probably does not persist northward in areas (such as Kentucky) where winters are sometimes severe (R. Cranfill 1980).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The name Thelypteris thelypterioides (Michaux) Holub has been applied to T. palustris, but A. F. Tryon et al. (1980) have shown that this was a result of an incorrect typification by C. V. Morton (1967).
Thelypteris palustris var. palustris occurs in Eurasia.
Varieties 2 (1 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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