Equisetum laevigatum A.Braun

  • Authority

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

  • Family

    Equisetaceae

  • Scientific Name

    Equisetum laevigatum A.Braun

  • Description

    Species Description - Stems 20–150 cm tall, 3–7 mm diam., unbranched except on damaged plants, yellowish green; sheaths with length:width ratio of 2:1 with black rim at distal edge, otherwise green; stomata in single lines, one line on each side of a groove; ridges 10–32, flattened to convex, smooth to tuberculate; sheaths green, elongate, 7–15 x 3–9 mm; teeth 10–32, each without articulation line but articulate and shedding early, leaving a dark rim on each sheath; stem cross sections (Fig. 144c) with prominent vallecular collenchyma extending to the vallecular canal; carinal collenchyma of lesser extent; endodermis of the double common type; strobili terminal on stems, ca. 10–20 mm long, apices rounded or each with a small apiculum; 2n=216 (USA).

  • Discussion

    Lectotype (chosen by Hauke, 1963: 67). U.S.A. “N. Riehl No. 279. Bords immediats du Mississippi, St. Louis, Mo., Juin 1840” (NY!).

    Equisetum kansanum J. H. Schaffn., Ohio Naturalist 13: 21. 1912. Type. U.S.A. Kansas: Clay County, Bloom Township, Engelmann s.n. (OS; isotype US).

    Unverified, Doubtful, or Mistaken Reports. NL (Aguirre C. 639, UNL, cited by Aguirre Clavera´n, 1983, but this is E. hyemale). Equisetum laevigatum is limited in Mexico to the northwestern states and is distinct by the stem ridges lacking prominent tubercles, cones rounded apically, teeth without conspicuous articulation, and prominent vallecular collenchyma. It crosses with Equisetum hyemale (E. xferrissii), which see for details. This species is an annual in Canada and the northern United States, but is perennial in Mexico.

  • Distribution

    Terrestrial in pine-oak forests; 1130–1850 m. W USA & Can; Mexico.

    Mexico North America| Canada North America| United States of America North America|