Callistopteris apiifolia, photographed by Joel Nitta.

Belongs within: Leptosporangiatae.
Contains: Hymenophyllum, Trichomanes.

The Hymenophyllaceae include the filmy ferns, mostly small ferns that get their vernacular name from their thin translucent fronds, with blades generally only one cell thick. Generic subdivisions within this family have varied significantly between authors, but most recent studies agree on a basal division between broad Hymenophyllum and Trichomanes lineages. One of the largest species of Hymenophyllaceae, the kidney fern Cardiomanes reniforme, has been suggested to be the sister of all other Hymenophyllaceae, but Pryer et al. (2001) resolved it as the sister to the Hymenophyllum lineage.

Characters (from Smith et al. 2006): Terrestrial and epiphytic; rhizomes slender, creeping, wiry, or sometimes erect and stouter, protostelic; vernation circinate; blades usually one cell thick between veins; stomata lacking; cuticles lacking or highly reduced; scales usually lacking on blades, indument sometimes of hairs; sori marginal, indusia conical (campanulate), tubular, or clam-shaped (bivalvate), with receptacles (at least in trichomanoid genera) usually elongate, protruding from involucres; sporangia maturing graduately in basipetal fashion, each with an uninterrupted, oblique annulus; spores green, globose, trilete; gametophytes filamentous or ribbon-like, often reproducing by fragmentation or production of gemmae; x = 11, 12, 18, 28, 32, 33, 34, 36, and perhaps others.

<==Hymenophyllaceae [Hymenophyllales, Hymenophylleae, Hymenophylloideae]
    |  i. s.: Hymenoglossum cruentumPS01
    |         Rosenstockia rolandi-principisPS01
    |         MeringiumDF97
    |           |--M. denticulatum [=Hymenophyllum denticulatum]I77
    |           |--M. holochilum [=Hymenophyllum holochilum]DF97
    |           |--M. meyenianum [=Hymenophyllum meyenianum]I77
    |           |--M. minimum [=Hymenophyllum minimum Rich. 1832]C49
    |           `--M. multifidumC49 (see below for synonymy)
    |         HopetediaSS04
    |  `--Cardiomanes Presl 1843PS01, A61 [Cardiomanoideae]
    |       `--*C. reniforme (Forster) Presl 1843A61 [=Trichomanes reniforme Forster 1786A61, Crepidomanes reniformeC06]
            |--C. apiifoliaI77 [=Trichomanes apiifoliumI77; incl. T. polyanthosB78]
            `--C. baueriana [incl. C. baldwinii, Macroglena toppingii]DF97

Meringium multifidumC49 [=Trichomanes multifidum Forster 1786C49, Hymenophyllum multifidum (Forster) Swartz 1801C49; incl. H. alpinum Col. 1899C06, H. oligocarpum Col. 1899C06, H. truncatum Col. 1891C06]

*Type species of generic name indicated


[A61] Allan, H. H. 1961. Flora of New Zealand vol. 1. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. R. E. Owen, Government Printer: Wellington (New Zealand).

[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.

[C49] Crookes, M. W. 1949. A revised and annotated list of New Zealand Filicinae. Transactions and Proceedings of the Royal Society of New Zealand 77 (2): 209–225.

[DF97] Dassler, C. L., & D. R. Farrar. 1997. Significance of form in fern gametophytes: clonal, gemmiferous gametophytes of Callistopteris baueriana (Hymenophyllaceae). International Journal of Plant Sciences 158 (5): 622–639.

[I77] Iwatsuki, K. 1977. Studies in the systematics of filmy ferns III. An observation on the involucres. Botanical Magazine, Tokyo 90: 259–267.

[PS01] Pryer, K. M., A. R. Smith, J. S. Hunt & J. Y. Dubuisson. 2001. rbcL data reveal two monophyletic groups of filmy ferns (Filicopsida: Hymenophyllaceae). American Journal of Botany 88 (6): 1118–1130.

[SS04] Schneider, H., E. Schuettpelz, K. M. Pryer, R. Cranfill, S. Magallón & R. Lupia. 2004. Ferns diversified in the shadow of angiosperms. Nature 428: 553–557.

Smith, A. R., K. M. Pryer, E. Schuettpelz, P. Korall, H. Schneider & P. G. Wolf. 2006. A classification for extant ferns. Taxon 55 (3): 705–731.

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