Synonym(s): Asplenium fragile C. Pres! var. insulare C. V. Morton; A. fragile sensu Hillebr., non C. Pres!; A. rhomboideum sensu W. J. Rob., non Brack.

Variety endemic

Peruvianus is the botanical Latin word used as an adjective for Peru, the type locality for the species. Latin insularis, pertaining to islands, insular.

Plants delicate, small to medium-sized, terrestrial.Rhizomes decumbent, 3-12 mm diam. Fronds 15-46 x 1-3 cm, often proliferous with 1 to many proliferations on upper stipes and lower rachises. Stipes around 115 frond length, dull gray or brown with 2 greenish ridges on adaxial surfaces, glabrous except for a few fine scales at very bases. Blades 1-pinnate, narrow, long-linear, narrower at bases, pale green to dark green; rachises thin, pale brown. Pinnae up to 35 pairs, alternate, uniform in shape, well separated at base of blade, closer distally, 4-15 x 4-12 mm, upper margins with 1-5 shallow, blunt-tipped lobes, almost all of the pinnae having a superior, acroscopic basal lobe. Veins pinnately branched. Sori fewer than 5 per pinna. Indusia thin.

A federally listed endangered species found in dark, moist areas, in rock crevices, or at the mouths or in remote comers of lava tubes that receive very little light, 1,650-2,200 m, on Maui and Hawai 'i.

Asplenium peruvianum is native to the Andes in South America. The Hawaiian variety appears to be larger and coarser, with thicker rachises, larger fronds, and almost all of the pinnae having a superior, acroscopic basal lobe. This taxon is part of a group of closely related species that needs further study in Hawai 'i as well as in the Andes.

This Hawaiian variety may represent a complex of two or more taxa: a delicate, usu-ally nonproliferous, longer, narrower, light green form often found in dark lava tubes, and a coarser, shorter, wider, dark green, almost always proliferous form possibly found in more open areas.

Asplenium peruvianum var. insulare, a 1-pinnate fern, may be distinguished by its habitat; narrow, long-linear, pale green fronds; dull gray or brown stipes with 2 greenish ridges on the upper surface; and occasional 1 to many plantlets on the upper stipes and lower rachises.