Hymenophyllales

Order Hymenophyllales

This group is known as the filmy ferns and bristle ferns, with a subcosmopolitan distribution. They are generally restricted to very damp places or to locations where they are wetted by spray from waterfalls or springs. Ferns in the Hymenophyllaceae have existed since at least the Upper Triassic

Ecology & Form

  • This groups contains both epiphytic and terrestrial plants

Sporophyte (spore-bearing phase)

Vegetative features

Stems

  • Stems are rhizomatous and scale-less

  • Rhizomes are slender and creeping or stout and erect

  • Protostelic

Leaves

  • Leaves are usually 1-cell thick, venation open, with stomata absent

  • Cuticle absent or reduced, blade scales usually absent

  • Trichomes are sometimes present

Roots

  • Adevnitious roots

Reproductive features

  • Sori are marginal, the receptacle elongate and continuous with vein tips.

  • Indusia are present and conical, tubular, or 2-lobed

  • Sporangia are basipetalous, dehiscence is uninterrupted, the annulus oblique

  • Spores are green, globose, and trilete.

Gametophyte (gamete-bearing phase)

  • Gametophytes are filamentous or ribbon-like, often reproducing by fragmentation or gemmae

Above: Ferns in the Hymenophyllaceae. A–C. Hymenophyllum tunbrigense. A. Plants growing on log. B. Leaf, adaxial surface. C. Leaf, abaxial surface, showing sori with bivalvate indusia. D,E. Hymenophyllum dilatatum, leaf and bivalvate indusium. F. Hymenophyllum flabelliforme, leaf. G,H. Trichomanes reniforme. G. Immature leaf; note open, dichotomous venation. H. Eruptive, elongate receptacles bearing leptosporangia. I,J. Trichomanes endlicherianum, showing elongate receptacles of sori. (Images A–C, from Vera Svobodova; D,E, H–J from Lawrence Jensen.)

Diversity

  • 1 family (Hymenophyllaceae); 2-9 genera; ~650 species

    • Hymenophyllum

    • Didymoglossum

    • Crepidomanes

    • Polyphlebium

    • Vandenboschia

    • Abrodictyum

    • Trichomanes

    • Cephalomanes

    • Callistopteris

Classification

└Tracheophytes

└Euphyllophytes

└Ferns (Polypodiopsida)

└Polypodiidae

└Hymenophyllales

Geologic Range

Above: Hopetedia praetermissa, a member of the Hymenophyllaceae, from the Late Triassic (Axsmith et al. 2001)