Diplopterygium
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Authority
Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
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Family
Gleicheniaceae
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Scientific Name
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Description
Genus Description - Terrestrial, commonly scandent; rhizomes long-creeping, cord-like, protostelic, bearing deciduous, lanceolate scales; fronds monomorphic, erect or scandent; blades pseudodichotomous at top of stipes, with an arrested scaly bud at the tip, this surrounded by scales, or this bud developed and the rachis ± indeterminate, continuing to produce two opposite pinnae over time, rachis eventually ending in an arrested bud; accessory branches (borne basiscopically at the base of a fork) absent; dormant buds with stipule-like outgrowths (pseudostipules); pinnae determinate, not forking, 2 to many opposite pairs, large, to several meters long, pinnate-pinnatisect to bipinnate, with alternating pinnate or pinnatisect pinnules, costae and costules sometimes bearing lanceolate or variously dissected scales and hairs, blade tissue sometimes glaucous; veins free, 1-forked; sori round, with or without paraphyses, of 2–4(–5) globose sporangia; indusia absent; spores tetrahedral, surfaces smooth or nearly so; x=56.
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Discussion
Lectotype (chosen by Christensen, Index Filic. LIV. 1906): Gleichenia glauca (Thunb. ex Houtt.) Hook. [= Polypodium glaucum Thunb. ex Houtt.] = Diplopterygium glaucum (Thunb. ex Houtt.) Nakai.
Diplopterygium comprises about 10 species, all in the Paleotropics (India to Japan and Malesia), except D. bancroftii. The genus is distinct from other genera of Gleicheniaceae by the large, bipinnate or pinnate-pinnatisect pinnae. In this character it resembles the Old World genus Gleichenia, which has much smaller, often bead-like or pouch-like ultimate segments. The penultimate divisions of Sticherus, Dicranopteris, and Gleichenella are all pinnatifid or pinnatisect. Diplopterygium also differs from both Dicranopteris and Gleichenella by the dormant buds with scales, rather than hairs, and by the 1-forked (vs. 2–4- forked) veins in the ultimate segments. Affinities of Diplopterygium are apparently not close to any of the other genera of Gleicheniaceae. For a discussion of the family relationships, see comments under Gleichenella.