Flora of the Hawaiian Islands
Literature for Asplenium caudatum
Brown & Brown, 1931; Copeland, 1932; Palmer, 2003; Brownsey, 1998; Lorence & Wagner, 2019; Salgado, 2020.
   Aspleniaceae -- The Spleenwort Family Bibliography
      Asplenium caudatum
General Information
DistributionSE Asia to Polynesia, but not New Zealand.
Epiphytic or terrestrial. Rhizomes stout, creeping or suberect, 1-1.5 cm in diameter with 7-30 fronds clustered distally, apex clothed with brown, clathrate, narrowly oblong or subulate scales 4-7(-15) mm long, 0.5-1 mm wide with entire margin.
Fronds with stipe (5–)28–40 cm long, 3–10 mm in diameter, dull dark brown, scaly or glabrescent, scales reddish brown to black, narrowly ovate-triangular to linear 5 mm long with subentire margin, mixed with smaller hairlike and irregularly branched appressed scales; blade (10–)41–150 cm long, (12-)14–16(-23) cm wide, narrowly oblong to linear-lanceolate, stiffly chartaceous or subcoriaceous, 1-pinnate-pinnatifid to 1-pinnate-pinnatisect, pinnae gradually reduced toward blade base, several basal pinnae sometimes reduced to ⅓ or less size of middle pinnae, narrowing gradually to pinnatifid apex, rachis not proliferous, usually covered with narrowly ovate-triangular scales with long filiform apex and spreading basal cilia similar to those on stipe; pinnae closely approximate, (9–)20–50 on each side, alternate, middle pinnae subsessile or on stalks 1–2 mm long, (2–)4–17 cm long, (0.6–)1–2.5 cm wide, oblong- to linear-lanceolate, narrow sinuses, divided about ½ width, lobes diverging at 20–45 degree angle from costae, segments acute to obtuse at apex, shallowly dentate, base narrowly cuneate, apex long and tapering, acroscopic basal lobe similar or slightly larger than the rest, not very distinct from other lobes, oblong or rounded in overall appearance, apex irregularly truncate and variabe, crenate or irregularly toothed, notch absent, costae and veins of with a few hairlike scales on abaxial side; veins at acute angle to costae, forking 2–3 times, ending in teeth near margin.
Sori, first line oblique and near or not to costae, alternate, 5–10 mm long, each pinna lobe also usually with 1–3 shorter sori 1.5–3 mm long facing each other; indusium brown with thin margin.
Asplenium horridum Kaulf. var. humile E. D. Br. seems to be a depauperate but fertile form of A. caudatum, as there are intermediate forms linking it with typical full-sized plants.
David Lorence