Synonym(s): A. horridum f. mirabile (Copel.) W. H. Wagner; A. truncatum Blume

Common names: 'iwa, 'alae

Indigenous

Latin horridus, bristly, rough, shaggy, alluding to the shaggy nature of the stipes and rachises.

Plants medium-sized, terrestrial. Rhizomes short-creeping to decumbent, up to 1.5 cm diam. Fronds 55-130 x 6-32 cm, not proliferous. Stipes dark brown, usually heavily covered with gray to black narrowly triangular scales, occasionally with few to no scales; glandular hair absent. Blades 1-pin-nate-pinnatifid to 1-pinnate-pinnatisect, linear-lanceolate, subcoriaceous, gradually reduced in width at base, narrowing gradually to tips, rachises usually covered with scales same as those on stipes. Pinnae 28-50 pairs, alter-nate, linear-lanceolate to Ianceolate, deeply lobed to nearly pinnatisect, lobes pointing out at 20-40° angle from costae, several basal pinnae tapering to 1/5 or less size of middle pinnae; lobe tips rounded, shallowly dentate to toothed; costae and veins with fine scales. Veins 1-to 2-forked. Sori in lines parallel and close to costae, alternate, often with a second group of sori in midparts of lobes. Indusia wide, lighter colored than blades.

Somewhat common terrestrial fern in wet, mesic to dry forests and mesic shrublands, 200-1,000 m, all major islands. Two varieties are found: one glabrous and the other quite hairy.

Several nineteenth-century authors stated that Asplenium horridum also grows in Java or Fiji, and many checklists have listed it as indigenous. This understanding of its distribution is maintained here. However, it has recently been noted that Asplenium horridum Brack. and A. caudatum G. Forst., a spe-cies with a wide distribution in the Pacific and in Southeast Asia, may in fact be conspecific. If this is correct the name A. cau-datum G. Forst. has priority because it was published first. To clarify this problem type specimens and collections of these taxa in the Pacific area will need examination and a literature review needs to be done. (Unfortunately deadlines for publication of this book did not allow time for this.) In any case the taxon remains an indigenous species.

Asplenium horridum, a 1-pinnate-pinnatifid ( -pinnatisect) fern, is characterized by its sori that are close and parallel to the costae (often with a second group in midpart of lobes); outward-facing, oblique pinna lobes; and usually heavy clothing of fine scales on the stipes and rachises (sometimes glabrous in var. glabratum).