Papuasian pteridophyte families

Hymenophyllaceae

Minute to moderate size epiphytes, terrestrial or rupestral or climbers starting from the ground, rhizome short and thick to long-creeping, sometimes filiform, bearing distichous fronds or radially symmetric, clothed with hairs, sometimes without roots. Fronds long-stipitate or not, lamina simple, bifid, palmatifid, pinnatifid to pinnately decompound, mostly 1 cell thick except at the veins, membranous and lacking stomata, ultimate segments mostly small, 1-veined, veins mostly free, false veins sometimes present. Sori marginal, terminal on the pinnules or on short lateral lobes, protected by an obconic or tubular and/or bivalved indusium (involucre), the receptacle capitate or columnar, sometimes exserted from the involucre, sporangia sessile to very short-stalked, clustered along the receptacle, annulus complete, oblique or almost transverse, the sporangia opening by a +/- longitudinal slit; spores trilete, tetrahedral or globose tetrahedral, lacking a perispore.

Distribution

A widespread, distinctive, predominantly tropical and southern temperature family of up to perhaps 40 genera (or as few as two depending on the generic concepts of authors), containing over 400 species. In Papuasia there are 20 of the genera in the narrow sense, covering c. 60 species.

Literature

Copeland, E.B. 1933. Trichomanes. Philip. J. Sci. 51: 119 - 280.

Copeland, E.B. 1937. Hymenophyllum. Philip. J. Sci. 64: 1 - 118.

Copeland, E.B. 1938. Genera Hymenophyllacearum. Philip. J. Sci. 67: 1 - 110.

Croxall, J.P. 1975. The Hymenophyllaceae of Queensland. Aust. J. Bot. 23: 509 - 547.

Iwatsuki, K. 1975. Studies in the systematics of filmy ferns. I. A note on the identity of Microtrichomanes. Brit. Fern. Gaz. 11: 115 - 124.

Iwatsuki, K. 1977. Studies on the systematics of filmy ferns. II. A note on the Meringium and the taxa allied to this. Gard. Bull. Sing. 30: 63 - 74.

Morton, C.V. 1968. The genera, subgenera and sections of the Hymenophyllaceae. Contrib. U.S. Nat. Herb. 38: 153 - 214.

Genera

1	Lips of indusium always well-developed, broader and longer than the hollow basal part; receptacle of sporangia usually much shorter than the lips of the indusium...	Hymenophyllum (c. 40)
	Indusium tubular or trumpet-shaped, sometimes with a 2-lipped mouth; receptacle usually elongating considerably and protruding from the old sori...	Trichomanes (c. 40)

Note

This is the simplest subdivision of the family. In each of these two genera there are several more or less homogeneous groups of species that have been given the rank of genus. These groups are readily evident with little dispute in Trichomanes but in Hymenophyllum the divisions are less clear-cut. In spite of this problem it seems preferable to divide the family fairly finely to avoid two large, heterogeneous genera. The Papuasian representatives can be separated by the following key, adapted freely from those of Copeland (1933, 1937, 1938):

Genera

1a.	Indusium clearly 2-lipped, sometimes tubular at the base, but then prominently 2-lipped in the upper portion (*Hymenophyllum s.l*)	2
	Indusium tubular or obconic, the margin entire or only slightly 2-lipped (*Trichomanes s.l.*)	7
2a.	Stellate or sometimes binate hairs present on most parts of the plant	Sphaerocionium (2)
	Hairs, if present, simple, not stellate	3
3a.	Receptacle indefinitely long, often protruding from sorus in fully mature fronds	4
	Receptacle fully included within the lips of the indusium, or nearly so	6
4a.	Lamina consisting entirely of flat teeth, or of flat teeth and a narrow wing	Myriodon (1)
	Lamina consisting of a continuous wing along the axes, sometimes with accessory wings perpendicular to the plane of the frond	5
5a.	Lamina winged only in the plane of the frond, the margins toothed	Meringium (c. 20)
	Accessory lamina wings or teeth perpendicular to the plane of the frond	Amphipterum (c. 4)
6a.	Margin toothed with sharp teeth	Hymenophyllum (c. 1)
	Margin entire or obscurely toothed	Mecodium (c. 15)
7a.	Rhizome relatively long-creeping, very slender	8
	Rhizome stout, and/or fronds clustered	13
8a.	Fronds simple or lobed to pinnatifid; false veinlets (thickened, +/- supportive tissue, independent of the axes) present between the true veins or as a continuous intramarginal line	Microgonium (c. 5)
	Fronds dichotomous to palmate or pinnate	9
9a.	Fronds dichotomous to palmate in plan, the axes sometimes proliferous	10
	Fronds pinnately divided, never proliferous	11
10a.	Margins or lamina bearing dark bristles	Microtrichomanes (1)
	Fronds glabrous, sometimes the axes proliferous	Gonocormus (2)
11a.	False veinlets present	Crepidomanes (c. 4)
	False veinlets absent	12
12a.	The band of tissue either side of the axes or veins thickened, the frond usually hairy, often glaucous	Pleuromanes (2)
	Axes not thickened, the frond not hairy or glaucous	Reediella (2)
13a.	Fronds simply pinnate, clustered on an erect caudex	Cephalomanes (c. 6)
	Fronds more compound, or if pinnate then the stipes spaced along the rhizome	14
14a.	Fronds finely divided, dissected into almost bristle-like segments	Macroglena (c. 4)
	Segments broader, soft	15
15a.	Rhizome elongate, stout, fronds remote, epiphytic or terrestrial	Vandenboschia (3)
	Rhizome shorter, erect, the fronds clustered, mostly terrestrial, or epiphytic and axes filamentous	16
16a.	Small epiphyte with filamentous axes; cells elongate transversely to costa	Abrodictyum (1)
	Larger ferns, epiphytic or terrestrial, axes rigid; cells not transversely elongate	17
17a.	Epiphytes or subepiphytes with large, tender, finely divided; stipes densely covered with bristles	Callistopteris (1)
	Terrestrial, with firm fronds; stipes naked or with scattered bristles	18
18a.	Axes usually copiously clad in trichomes; lamina lanceolate or ovate; ultimate segments not curling when dry	Nesopteris (1)
	Axes lacking copious trichomes; lamina deltoid, ultimate segments tending to curl under when dry	Selenodesmium (1)

Note

In a recent revision of the Hymenophyllaceae of Queensland (Croxall 1975), a combination of the above two treatments was presented: all the genera of the Hymenophyllum group combined under a broad Hymenophyllum and the genera of the Trichomanes group kept separate, with the exception of Vandenboschia which is combined with Trichomanes. This may be a more realistic view of the family. So far, chromosome studies have shed little light on this problem.

Updated November 1999 by Jim Croft (jim.croft@environment.gov.au)