Selaginella extensa Underw.

  • Authority

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

  • Family

    Selaginellaceae

  • Scientific Name

    Selaginella extensa Underw.

  • Description

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    Species Description - Stems long-creeping, forming loose mats to 35 cm long, radially symmetric, 0.4–0.6 mm diam., not articulate, not flagelliform, not stoloniferous, 2–3 times branched; rhizophores throughout, 0.2–0.3 mm diam.; leaves of one kind (isophyllous) throughout stem length, lustrous, dark green or brownish to brownish with red spots when old, linear-lanceolate, 1.8–2.2 x 0.2–0.3 mm, bases truncate or cuneate, abruptly adnate to the stems, glabrous or pubescent, margins greenish, denticulate, teeth hyaline, apices acuminate to short-aristate, aristae greenish hyaline, 0.1–0.2 mm long; strobili frequently in pairs at branch tips, quadrangular, 0.5–2(–2.5) cm long; sporophylls monomorphic; megasporangia scattered on ventral rows; microsporangia in two dorsal rows and scattered on ventral rows; megaspores deep yellow, rugose-reticulate, with a prominent equatorial flange, the flange often appearing to have tuberculate to papillate projections, 300–360 µm diam. (–400 µm diam. including equatorial flange); microspores orange.

  • Discussion

    Bryodesma extensa (Underw.) Soja´k, Preslia 64: 154. 1992. Type. Mexico. San Luis Potosi´: Las Canoas, Pringle 3900 (NY!; isotype DS!, MEXU, NY!, UC!, YU!).

    Unverified, Doubtful, or Mistaken Reports. Pue (Sharp 45375, US, cited by R. Tryon, 1955, but not verified). Selaginella extensa is one of the most distinct spikemosses in Mexico. It is characterized by forming long, loose mats that frequently are epiphytic or on rocks, by lustrous linear-lanceolate leaves that frequently have reflexed apices, and by lanceolate sporophylls with long-acuminate, green apices. Megaspores of this species are remarkable by their discoid-ovoid shape and prominent equatorial flange, which is erose and appears to have tuberculate to mamillate projections. This species is most closely related to the western North American S. oregana D.C. Eaton, but it can be distinguished from that by its appressed (vs. mostly spreading) leaves with truncate to cuneate (vs. decurrent) bases.

  • Distribution

    Epipetric in limestone crevices and cliffs or epiphytic on tree trunks and branches; 700-2100 m. Mexico.

    Mexico North America|