Plants forming diffuse or dense clones. Roots arising at nodes. Petioles 2--20 cm, sparsely pubescent. Pinnae 4--19 × 4--16 mm, pubescent to glabrous. Sporocarp stalks erect, unbranched, attached at base of petiole (occasionally up to 3 mm above it), not hooked at apex, 0.5--25 mm. Sporocarps perpendicular or slightly nodding, 3.6--7.6 × 3--6.5 mm, 1.5--2 mm thick, elliptic to nearly round in lateral view, pubescent but soon glabrate, scars left by fallen trichomes often appearing as purple or brown specks; raphe 1.1--1.7 mm, proximal tooth 0.3--0.6 mm, blunt, distal tooth 0.4--1.2 mm, acute, often hooked at apex. Sori 14--22. Sporocarps produced spring--fall (Apr--Oct). Widespread and variable; in ponds and wet depressions and on river floodplains; 0--2300 m; Alta., B.C., Sask.; Ariz., Ark., Calif., Colo., Idaho, Iowa, Kans., La., Minn., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., Oreg., S.Dak., Tex., Utah, Wash., Wyo.; Mexico; South America in Peru. A number of segregate species have been named and recognized in regional floras in North America: Marsilea mucronata A. Braun (less hairy, found east of Rocky Mountains), M . uncinata (glabrous, sporocarp stalks long, distal tooth of sporocarp hooked, south central United States), M . tenuifolia (pinnae very narrow, central Texas), and M . fournieri (small plants and pinnae, southwest). The features upon which these species are based intergrade into one another. The species are therefore best treated as conspecific with M . vestita (D. M. Johnson 1986). Putative hybrids between Marsilea macropoda and this species are discussed under the former.

Rhizome rooting only at the nodes; lfls appressed- hairy on both sides, the emergent ones 5-20 נ5-15 mm, spatulate to flabellate, slightly oblique, at least the inner margin usually concave; peduncle 2-25 mm, usually unbranched, attached at or to 3 mm above the base of the petiole; sporocarp 3.5-7.5 נ3-6.5 mm, the inferior tooth 0.3-0.6 mm, the superior one 0.4-1.2 mm and often hooked; sori 14-22 per sporocarp, with 27-64 microsporangia and (2-)9-15 megasporangia per sorus. Cordilleran region of w. U.S. and adj. Can. and Mex., e. to Minn., Io., and La. (M. mucronata) Ours is the widespread var. vestita.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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