Marsilea vestita Hook. & Grev.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Rhizome rooting only at the nodes; lfls appressed- hairy on both sides, the emergent ones 5–20 × 5–15 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 × 3–6.5 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.