Marsilea vestita

Marsilea vestita Hook. & Grev.
(Latin: vestis, garment, clothing, covering, = covered, apparently in reference to the sparse hairs on the pinnae of some individuals)

Local names: hairy water-clover, hooked pepperwort, water-clover, hairy pepperwort, narrow-leaf pepperwort

Petioles 2–20 cm long; pinnae 4–19 mm long, 4–16 mm wide, varying in appearance, typically 1–2 times as long as wide, fan-shaped or broadly cuneate, apically entire or undulate- crenulate, but sometimes (when growing submerged) narrow in appearance, 3–7.5 times as long as wide, narrowly and obliquely cuneate, apically irregularly toothed or crenulate; petioles 2–20 mm long; sporocarp stalks unbranched, with 1 sporocarp per stalk; sporocarps 3.6–7.6 mm long, 3–6.5 mm wide, pubescent with appressed hairs or soon typically glabrate (leaving purple or brown speck-like scars), with noticeable distal tooth; 2n = 40 (Lesho 1994). Ponds, wet depressions, along streams and rivers; widespread in TX except absent from most of the Pineywoods (e.g., Burnet Co., L.L. Sanchez 4038; El Paso Co., R.D. Worthington 4951, both BRIT); sw Canada throughout w U.S. e to MN, AR, and LA and extending in the se U.S. e to FL; also Mexico and Peru in South America. Sporocarps produced Mar–Oct. [M. mucronata A. Braun, M. uncinata A. Braun, M. tenuifolia Engelm. ex A. Braun, M. vestita subsp. tenuifolia (Engelm. ex A. Braun) D.M. Johnson] Plants with narrow pinnae are usually easily distinguished in the field and have sometimes been treated as a separate species (M. tenuifolia—e.g., Correll & Johnston 1970) or subspecies (M. vestita subsp. tenuifolia— e.g., Johnson 1986; Kartesz 1994; Diggs et al. 1999). However, this variant was not formally recognized by Johnson (1993a), Jones et al. (1997), or Kartesz (1999), and according to J. Peck (pers. comm.), it is an environmentally induced form that occurs when leaves develop submerged. We are therefore including it in M. vestita. Such variation is not surprising since the leaves of Marsilea species are known to “show great plasticity of form in response to a wide range of physical and chemical stimuli” (Johnson 1993a). Bob O’Kennon (pers. comm.), however, has noted populations in Gillespie Co. with very narrow leaves in locations where the plants are never submerged. Correll (1961) wrote a paper indicating that he had found Marsilea Mexicana, A. Braun (now recognized as M. ancylopoda A. Braun) new for TX, based on a specimen from Aransas Co. (Correll & Johnston 17623, TEX-LL); however, that specimen has since been identified as M. vestita (by D. Lemke in 2007), and M. ancylopoda is not known for TX.

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