Pterozonium steyermarkii Vareschi

  • Authority

    Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.

  • Family

    Pteridaceae

  • Scientific Name

    Pterozonium steyermarkii Vareschi

  • Description

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    Species Description - Rhizomes erect or ascending, short, ca 5 mm diam, densely hairy at the apex, the hairs setiform, brown or black; fronds simple, 2.5-16 cm long; stipes about equaling the laminae, thin, ca 0.5 mm diam, glabrous, shining, greenish or brownish towards the base, winged distally above the wing vertical towards the stipe apex, horizontal at the middle and towards the stipe base; laminae papery, spathulate-elliptic or narrowly oblanceolate, 2-10 cm long, 5-12 mm wide, 4-6 times longer than wide (the juveniles comparatively shorter), the apex obtuse or rounded, deep green above, paler beneath in life, drying gray-green with the primary veins sometimes stramineous; veins pinnate-flabellate, immersed above, prominulous beneath; sori submarginal, round, short, or elongate, discrete, terminal on the veins, parallel or at an angle to the margins; sporangia short-pedicellate, annuli 18 to ca 22 cells, the cells of the stomium similar but broader and thicker; paraphyses lax, twisted, catenate, about 20 cells long, on receptacles and on pedicels of the sporangia; spores sharply tetrahedral.

    Distribution and Ecology - In shaded, generally moist crevices of boulders and ravines of the Chimanta Massif in the eastern portion of the Guayana Highland.

  • Discussion

    Chimanta Massif, Torono-tepui, summit, along Cano Mojado, alt 1895- 1910 m, Steyermark & Wurdack 1059 (holotype V E N not seen, isotypes NY , US).

    Pterozonium steyermarkii is the only known simple-bladed species of the genus with narrow fronds 4-8 times longer than wide. The juveniles (Steyermark 75953, U S ) , which may be only 1—4 times longer than wide, usually have elliptic laminae broadest near the middle and tapering towards the apex of the fronds. They can be confused only with juveniles of P. eyclophyllum (Steyermark 75856), which are invariably oblanceolate, rounded at the apex, and broadest towards the frond apices