Osmunda

  • Authority

    Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.

  • Family

    Osmundaceae

  • Scientific Name

    Osmunda

  • Description

    Genus Description - Terrestrial, of moist habitats; rhizomes horizontal to usually erect, stout, surrounded by persistent, tough leaf bases and a wiry dense root mantle, caudices often subterranean or partly aerial, usually dichotomously branched or with a single arborescent trunk, apices lacking scales, but sometimes hairy; stipes not articulate, bases somewhat flared or expanded just above base to form sheathing, stipule-like wings; fronds crown-forming, dimorphic or hemidimorphic, sporophylls taller and more erect, croziers circinate, clothed with matted white to brownish hairs; sterile blades (or sterile portions) pinnate-pinnatifid to 2(–3)- pinnate, rarely 1-pinnate, laminae glabrous but axes densely hairy, especially at pinna bases and in young fronds; veins of sterile fronds (or sterile portions) free, simple or several times forked; fertile blades (or fertile portions) usually 2-pinnate, lacking green lamina, sporangia borne in dense paniculate clusters on ultimate veinlets; sporangia large, globose, splitting longitudinally across the distal end, with short, many-rowed stalks; spores green, short-lived, tetrahedral-globose, surface densely rugose or echinate; gametophytes epigeal, green, flat, cordate to elongate, the center thickened; x=22.

  • Discussion

    Lectotype (first chosen by Le´man?, Dict. Sci. Nat. 37: 9. 1825): Osmunda regalis L.

    Osmundastrum C. Presl, Gefa¨ssbu¨ndel Farrn 18. 1847. Type: Osmundastrum cinnamomeum (L.) C. Presl [= Osmunda cinnamomea L.]. For details of typification of these names, see Pichi Sermolli, Webbia 26: 506. 1972.

    Osmunda is subcosmopolitan, with about 10 species in temperate and subtropical regions. It occurs mostly in marshes, swamps, and other wet areas. The two Mexican species are very widespread, but relatively uncommon, except locally in suitable habitats. They are occasionally segregated into two genera. The other two genera in the family, Todea (South Africa and Australasia) and Leptopteris (Australasia) have sporangia borne on relatively unmodified pinnae. Osmunda is distinct by its dimorphic or hemidimorphic fronds more than once-pinnately divided, free veins, rhizome indument of hairs, green, globose spores, and nearly unique (in the ferns) chromosome base number. The family Osmundaceae is isolated phylogenetically and has an extensive fossil record dating back to the Carboniferous. Recent molecular studies indicate that the family is basalmost within the leptosporangiate ferns and forms the sister group to all other extant familes in the clade (Pryer et al., 1995, 2001). The eusporangiate ferns (Marattiaceae and Ophioglossaceae), plus Psilotaceae (whisk ferns) and Equisetaceae (horsetails) insert below the leptosporangiate ferns in most recent analyses based on molecular data