Marsilea L.
Descripción
Aquatic, subaquatic, or amphibious, forming diffuse or dense colonies, usually rooted, or entire plant floating; rhizomes shortto long-creeping, slender, with lateral shoots arising at nodes, bearing hairs; roots adventitious, thread-like, present only at nodes or also on internodes; leaves monomorphous, but emergent ones often somewhat different from floating or nonemergent ones, distichous, generally less than 30 cm long; stipes slender, upright or decumbent, glabrous or hairy, bearing at the apex two pairs of cuneate-flabellate leaflets that are pulvinate at the base; leaflets (pinnae) dichotomously veined, the veins anastomosing regularly, especially near the margin, forming a reticulum with elongate areoles; lateral margins of leaflets concave, straight, or convex, terminal margin entire or denticulate; indument of rhizomes, leaves, and sporocarps often with 2–9-celled uniseriate trichomes; fertile leaves usually terrestrial, with branched or unbranched peduncles bearing hardened, globose or discoid, nut-like sporocarps at the tips and diverging from the stipe at or above its base; sporocarps attached laterally or terminally to peduncles, which may be adnate for a short distance to the sporocarp (the adnate portion called a raphe), peduncles often ending in a blunt tooth, an additional superior tooth sometimes present; sori enclosed in sporocarps, disposed in two rows, sausage-shaped, with microsporangia borne along the margins of the sori and megasporangia borne medially, sori attached by a thin medial membrane to an elongate gelatinous mass (sorophore); sporangia hyaline, lacking annuli; microspores 16–64 per sporangium, white or pale brown, tetrahedral, smooth or variously ornamented; megaspores one per sporangium, ovoid, white, surface smooth or indistinctly reticulate; x=20.
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Forma de vida
Hidrófita enraizada, Hidrófita libreA
Distribución
México (país) Nativo y no endémicoA
Categoría IUCN
No incluidaB
Categoría NOM-059-SEMARNAT-2010
No incluidaC
Discusión taxonómica
Marsilea comprises 45 to 70 species, and is subcosmopolitan, but primarily in temperate areas and subtropical areas; the greatest number of species is found in Africa and Australia. The species grow in ephemeral pools in drier areas (seasonally wet habitats), savannas, wet ditches, along creek and river margins, or in permanent pools and marshes. The New World species, nine native and two naturalized, were monographed by Johnson (1986), and our treatment is based primarily on this work. Seven species occur sporadically in Mexico. Non-reproductive specimens can be difficult or impossible to identify, and some populations apparently remain vegetative for long periods.
Sporocarps of Marsilea often have great longevity. Johnson (Amer. Fern J. 75: 30. 1985) was able to grow sporophytes of M. mollis from sporocarps taken from a herbarium specimen that had been dry for 89 years. Sporocarps of Marsilea are known to be transported by waterfowl, on muddy feet, or may be ingested and passed intact through digestive tracts (Johnson, 1986: 24). The sporocarps of an Australian species, M. drummondii A. Braun, commonly called nardoo, are ground into flour by Aboriginals, then mixed with water to form an edible paste.
The Marsileaceae were once thought to be related to the Schizaeaceae, but molecular and fossil evidence now suggests that the family is most closely allied and sister to the two other heterosporous fern families, Salviniaceae and Azollaceae (Pryer et al., 1995; Rothwell & Stockey, 1994).
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Sporocarps of Marsilea often have great longevity. Johnson (Amer. Fern J. 75: 30. 1985) was able to grow sporophytes of M. mollis from sporocarps taken from a herbarium specimen that had been dry for 89 years. Sporocarps of Marsilea are known to be transported by waterfowl, on muddy feet, or may be ingested and passed intact through digestive tracts (Johnson, 1986: 24). The sporocarps of an Australian species, M. drummondii A. Braun, commonly called nardoo, are ground into flour by Aboriginals, then mixed with water to form an edible paste.
The Marsileaceae were once thought to be related to the Schizaeaceae, but molecular and fossil evidence now suggests that the family is most closely allied and sister to the two other heterosporous fern families, Salviniaceae and Azollaceae (Pryer et al., 1995; Rothwell & Stockey, 1994).
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