A fern that grows on stone walls and other surfaces, with a few elongated fronds. It is easy to distinguish because the fronds are long, thin, and few in number. The rhizome is short and creeps laterally, and the leaves are dense. The fertile fronds are much taller and thinner, reaching up to 15 cm in sterile fronds and 49 cm in fertile fronds. The petiole is thin, hard, wiry, and blackish, making up about half of the entire leaf. The fronds are once-pinnate, with only a few subordinate pinnules. At most, there are 2-3 pairs of sub-pinnules that remain constant in size, with a terminal pinnule of the same length attached at the apex. In well-developed fronds, an additional sub-pinnule emerges from the base of the lowermost side sub-pinnule. The base of the sub-pinnules merges with the rachis, and green leafy tissue appears on the rachis between the sub-pinnules. The individual pinnules are elongated and roughly linear, with slightly inflated basal lobes on the underside of lateral pinnules. The fronds are thin but tough. Fertile fronds are nearly the same shape and are about twice as narrow. Sterile fronds have rough serrations, but fertile fronds are smooth.