Aquatic and Wetland Vascular Plants of the Northern Great Plains
4. Polypodiaceae, the Polypody Family
6. Thelypteris Schmidel1. Thelypteris palustris Schott -- Marsh fern
Rhizomes spreading and branching, slender, with a few appressed scales. Fronds annual, only slightly dimorphic, mostly erect, the blades pinnate-pinnatifid, lanceolate or oblong-lanceolate, 15-30(40) cm long, 8-15(20) cm wide, puberulent on the rachis and midveins, acuminate, only slightly narrowed at the base; pinnae usually 10-25 pairs, spreading, mostly alternate, 8-15(20) mm wide; petioles scaleless. Sterile fronds thin, delicate, pinnules broadly oval, obtuse, 3-5 mm wide, veins once-dichotomous; petioles shorter to longer than the blade. Fertile fronds surpassing the sterile ones, more firm than the sterile fronds, the petiole longer than the blade; pinnules oblong, 2-4 mm wide, the margins revolute; veins simple or once-dichotomous; sori round, usually confluent on the back of the pinnules; indusium attached at its center in the middle of the sorus, irregular in shape, usually ciliate. Jun--Sep. Boggy or marshy places, where water is fresh; scattered from ND to NE, especially common in the Sand Hills; (Nearly cosmopolitan; in N.Amer., Newf. to Man., s to GA and OK).
North American plants are var. pubescens (Lawson) Fern.
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| A frond of Thelypteris palustris. |
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