Adiantum obliquum Willd.

  • Authority

    Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.

  • Family

    Pteridaceae

  • Scientific Name

    Adiantum obliquum Willd.

  • Description

    Species Description - Rhizome short-creeping, 2-4 mm diam.; rhizome scales lustrous yellow-brown, denticulate, lanceolate, 2.5-3.0 mm long, 0.5 mm wide, margin with short teeth; fronds clumped, 25-45 cm long, 7-10 cm wide; stipe ca. ½ the frond length, black, lustrous, glabrous with rare pectinate scales (to 2 mm long); blade oblong to oblong-deltate, pinnate with 6-9 pairs of pinnae, terminal pinnule conform, the basal pinnae often largest, short-stalked, inequilateral; rachis with dense, pectinate scales; largest pinnules 35-40 mm long, with apex long-acuminate, base oblique, margin finely denticulate to unevenly biserrate, midvein close to middle of pinnule, upper surface glabrous, with idioblasts, lower surface glabrous or with rare, pectinate, hairlike scales; sori several along both margins 1-6 mm long; indusium minutely denticulate, glabrous or with short hairs (0.1 mm long); spores whitish-cream.

  • Discussion

    Lectotype (chosen by Lellinger, Mem. New York Bot. Gard. 23: 13. 1972). Venezuela. Caracas, Bredemeyer s.n. (B-Willd. 20067-1!). The once-pinnate species (A. obliquum—petiolatum complex) are in need of careful revision over their entire range of Middle America, West Indies and South America. Adiantum petiolatum Desvaux (in the sense of A. R. Smith, 1981) with its long-creeping rhizome may be a distinct species or may be conspecific with A. obliquum. The Oaxacan material of A. obliquum is distinguishable by its once-pinnate fronds, dense pectinate rachis scales, blades broadest at or near the base, large pinnules with long-acuminate tips and whitish-cream spores (which can barely be seen when on herbarium paper). Adiantum obliquum and A. amblyopteridium may have formed the fertile hybrid A. oaxacanum (q.v.), which is intermediate in morphology. Younger plants of A. oaxacanum occasionally have fronds with only the basal pinnae further pinnate. The rounder apices, reduced basal pinnules, and tan spores (easily seen against herbarium paper) distinguish A. oaxacanum from A. obliquum.

  • Distribution

    Terrestrial, in wet, lowland forests; Choapan, Juchitán, Pochutla, Tuxtepec, Villa Alta; 100-600 m. Mexico (Ver, Oax, Chis, Tab); Guat to Pan; WI, Trin, Tob; Ven & Col to Bol & Braz.

    Mexico North America| Brazil South America| Bolivia South America| Colombia South America| Venezuela South America| Trinidad and Tobago South America| Panama Central America| Guatemala Central America|