Erect ground ferns, or scandent epiphytes starting from the ground; rhizome with peltate-based scales, long-creeping, or short and erect and bearing stolons, dictyostelic. Fronds short- or long-stipitate, vascular bundles 1,2 or several, arranged in a V- or U-shape, lamina simple or pinnate, the pinnae articulate to the rachis, glabrous or sometimes finely hairy, veins 1 -2 ( - 3)-forked, free, terminating short of the margin or at the margin. Sporangia in discrete round sori in a single row either side of the midrib, superficial or terminal on a vein, or elongate-marginal and served by several veins, mostly with a round-reniform indusium opening outwards, or an elongate-marginal indusium opening outwards, or exindusiate; annulus longitudinal, interrupted; spores monolete.
A family of 4 genera with c. 120 species from most of the tropical and subtropical regions of the world. Three genera with c. 25 species occur in Papuasia; only Nephrolepis could be considered aquatic.
Terrestrial, subepiphytic or epiphytic ferns of small to large size. Rhizome compact, +/- erect, densely clothed in brown, non-clathrate, peltat-based, pale-edged, often hairy scales, radially symmetric with close fronds each associated with a slender, root-bearing, often proliferous runner, the caudex sclerotic, dictyostelic, the runner portostelic. Fronds long stipitate, the stipes not articulate to the rhizome, fibro-vascular bundles 6 or more, arranged in a U-shape, the 2 adaxial bundles larger; the lamina long and narrow, pinnate, the pinnae sissile, articulate to the rachis, the apical pinnae gradually reduced, chartaceous to sub coriaceous, paleate, hairy, or glabrescent, costate, the costa adiaxially grooved, margin entire to slightly crenate or lobed, veins free, simple or more often 1 - 3-forked, one vein group in each crenation, each branch terminating in a conspicuous intra- or submarginal hydathode, often visible as a white scale on the adaxial surface. Sporangia arranged in sori terminal on the veins, submarginal or intramarginal, generally discrete, round and served by a single vein, or elongate along the margin and served by several veins, indusium extrorse, round-reniform attached at the sinus, or roundsih and attached across a broad base, or elongate along the margin, pedicel long, 3-seriate, annulus longitudinal, interrupted, on 12 - 14 thickened cells. Spores monolete with an irregularly roughened surface, translucent.
Distribution: A pantropical genus of c. 30 species with c. 10 species in Papuasia. Most of these are either terrestrial or epiphytic, however two species are sometimes found in association with swamp vegetation.
Croft, J.R. 1985. Ferns and Fern Allies, in Leach, G.J. & Osborne, P.L. 1985. Freshwater Plants of Papua New Guinea. 33 - 74, f. 6 - 13, pl. 5 - 7.
Holttum, R.E. 1954 (revised 1965). Ferns of Malaya. A revised flora of Malaya. Volume 2. Govt. Printer, Singapore. 1 - 643. (Nephrolepis radicans p. 381).
|1||Longest pinnae c. 3 cm long, apices rounded; stolons a major part or the plant, producing small plants at regular intervals; sori marginal or submarginal…||N. radicans|
|Pinnae c. 7 cm long or longer, apices tapering; stolons less dominant; sori +/- midway between midrib or pinna and the margin…||
Caudex short, erect, clothed in overlapping dark scales with pale margins, runners thiner than stripes, not scandent, occasionally producing new plants. Stipes 20 - 50 cm long, lamina 1 -2 m long, 15 - 20 cm wide, gradually narrowed towards the apex, the basal pinnae slightly reduced, shortened and spaced out, longest pinnae fairly tough, +/- oblong, 8 - 15 x 1 - 2.5 cm, tapering and +/- pointed apically, sometimes +/- curved, base truncate or rounded, sometimes with a slight acroscopic lobe, margin with blunt rounded teeth to almost entire, minutely scaly when young, glabrescent; veins 1 -2-forked and ending in small hydathodes near the margin, the hydathodes often visible as white dots on the upper surface. Sori well within the margin medial, induium +/- cicular with a narrow sinus.
Habitat: Found in a wide range of situations from swamps and swamp or river margins, mangrove forests to ridge crests, or epiphytic, in the deep shade of the forest or in open situations. Common in distributed areas and in regrowth conditions or on forest-grassland margins. At low elevations from sea level to 1200 m altitude.
Distribution: Throughout the lowland tropics of the world. In Papuasia this species has been collected from most of the lowland regions.
Notes: The field notes of two specimens from the Sepik region indicate that the young fronds are boiled and eaten as a green vegetable.
This species appears very closely related to another that has been referred to as Nephrolepis acuminata (? = N. davallioides) in Papuasia. It occurs in a similar range of habitats but is more commonly epiphytic. It differs from this species in the position of sori on small, rounded marginal lobes. However, there are specimens that are difficult to place in either group with certainty; there may be hybridism or other species involved.
Specimens from well-shaded situations have larger fronds with broader pinnae.
Caudex short, erect, clothed in overlapping dark scales with pale margins, runners about as thick as stipes, long and climbing, producing short, scaly, frond-bearing caudices at regular intervals. Stipes 5 - 20 cm long, lamina 30 - 60 cm long, 3 - 5( - 8) cm wide, gradually narrowed towards the apex, the basal pinnae slightly reduced, shortened and spaced out, longest pinnae fairly tough, +/- oblong, 15 - 30 x 7 - 12 mm, slightly tapering and rounded apically, base truncate with a slight acroscopic lobe, margin with a few very shallow teeth towards the apex, minutely scaly when young, glabrescent; veins 1 - 2-forked and ending in small hydathodes near the margin. Sori just within the margin, indusium +/- circular with a narrow sinus.
Habitat: Open situations or scrub in more or less full sun, swamp margins and floating root-mat vegetation, at low elevations to c. 70 m altitude. Not always restricted to swamps.
Distribution: Burma and Indochina through Malesia to the Philippines and New Guinea. Not often collected on the New Guinea mainland, known from the Morobe and Western provinces, but to be expected elsewhere.
Notes: The stout, scandent runners of this species producing small plants at regular intervals are the most reliable distinction from the other species of Nephrolepis; the small rounded pinnae are also distinctive.