A TAXONOMIC REVISION OF HYMENOPHYLLACEAE

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BLUMEA — Vol. 51, No. 2, 2006
14a. Blades once-pinnate to bipinnatifid . . . . . . . . . . . . . . . . . . . . . 8. Cephalomanes
b. Blades bipinnate or more divided . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
15a. Long bristle-like light reddish hairs (Fig. 2h) present on stipes and rachises . 16
b. Long bristle-like light reddish hairs absent on stipes and rachises . . . . . . . . . 17
16a. Laminar cells reduced (Fig. 2i). Less than 3 rows of cells between midribs and
margins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Abrodictyum
b. Laminar cells not reduced. More than 3 rows of cells between midribs and margins
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. Callistopteris
17a. Laminae more than one cell thick . . . . . . 7. Trichomanes (subg. Davalliopsis)
b. Laminae one cell thick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
18a. Laminar cell-walls thin and straight . . . . 2. Crepidomanes (subg. Nesopteris)
b. Laminar cell-walls slightly or quite thick, wavy or pitted . . . . . 6. Abrodictyum
1. HYMENOPHYLLUM
Hymenophyllum Sm. (1793) 418. — Lectotype: Hymenophyllum tunbrigense (L.) Sm. (selected by
Presl (1843) 31).
Rhizomes long-creeping, frequently branching, usually filiform or wiry, up to 2 mm
diam., nearly glabrous or sparsely covered with multicellular hairs (exceptionally
densely covered with hairs in subg. Fuciformia), protostele subcollateral, dorsiventral,
or ‘reduced’ (with more or less central xylem-like parenchyma), cortices heterogeneous,
with few and fine roots. Stipes various in length, at a distance from the adjacent ones.
Blades usually pinnate to quadripinnate or occasionally simple, 165 by 17 cm, venation
anadromous, laminae usually one cell thick, but sometimes two or more cells thick.
Sori paratactic, lips usually bivalvate, receptacles usually included in involucres.
Distribution — Throughout the tropics to temperate regions; c. 250 species.
Habitat — Usually low- to middle-epiphytes on tree trunks, sometimes canopy sunepiphytes,
occasionally epilithic or terrestrial.
Chromosome base number — Various, x = 11 to 36.
Note — Hymenophyllum in our sense stands as the largest genus of Hymenophyllaceae,
and almost corresponds to Hymenophyllum in the traditional and broad sense
but also includes some taxa formerly regarded as Trichomanes s.l. Iwatsuki (1984)
segregated Sphaerocionium, which is characterized by distinctive stellate hairs, from the
remaining Hymenophyllum (s.l.) taxa. Recent studies (Hennequin et al., 2003, in press)
suggest that Sphaerocionium is nested within Mecodium, another easily recognizable
group of Hymenophyllum s.l., as currently defined. Under our strategy of classification
– making each taxon a natural group – Sphaerocionium is to be treated as a genus,
species belonging to Mecodium should be split into more than two genera. To avoid
such inconvenience, all species of Hymenophyllum s.l. are placed in our Hymenophyllum.
Because the systematic relationships within this genus are not fully clarified, the
current revision treats only subgenera, with each subgenus monophyletic based on our
latest study using molecular data (Hennequin et al., in press).