synonym(s): Asplenium camptorachis sensu auct., non Kunze; A. erectum var. macraei (Hook. & Grev.) Hillebr.; A. erectum var. microphyllum Hillebr.; A. erectum var. myriophyllum Hillebr.; A. erectum Bory subsp. sphe-nolobium Zenker; A. erectum var. subbipinnatum Hillebr.; A. lunulatum Sw. var. macraei (Hook. & Grev.) C. Chr.; A. macraei var. angustlfolium Hieron.; A. macraei var. myriophyllum Hillebr.; A. macraei var. originaria Heiron.; A. macraei var. rapense E. D. Br. & F. Br.; A. macraei Hook. & Grev. f. sphenolobium (Kunze) Skottsb.; A. macraei f. strictum (Brack.) Skottsb.; A. macraei var. stricta (Brack.) Hieron.; A. macraei f. subbipinnatum (Hillebr.) Skottsb.; A. rhizophyllum sensu A. Heller, non Kunze; A. sphe-nolobium Zenker var. diplazisora Hieron.; A. strictum Brack.; Darea pectinata Sm.

Endemic? 'iwa 'iwa lau li'i (lau, leaf, · li'i, small: small-leaved 'iwa 'iwa) (P. & E.)

Name honors James Macrae (died 1830), who collected plants in Hawai 'i in 1825 as botanist on the Blonde under .Capt. Anson (Lord Byron).

Plants small to medium-sized, terrestrial, extremely variable in morphology. Rhizomes decumbent, with 16-60+ fronds or stipe bases clustered at apex. Fronds erect, 15-40 x 1.5-3 cm, never proliferous. Stipes round, 1/10-1/5 frond length, dark brown, 0.8-1.2 mm diam. near base, with narrow, thin, greenish wings on either side of adaxial surface. Blades 1-to 3-pinnate, linear to linear-lanceolate, medium to dark green, chartaceous to subcoriaceous; rachises dark brown, winged as on stipes. Pinnae 22-45 pairs, short-stalked, alternate, extremely variable in size and shape, ranging from simple and entire to deeply dissected, rectangular to triangular, 6-15 x 3-13 mm, tips obtuse, margins entire to 5-8 deep lobes on distal margins to again 2-pinnate and deeply dissected into narrow segments, acroscopic basal margins parallel with rachises, basiscopic margins deeply incised near base. Ultimate segments on deeply cut forms narrow, with 2 (-4) apical teeth. Veins forked proximally, unforked distally. Sori usually more than 8 per pinna, linear, medial to pericostal. Indusia thin.

Common in mesic to wet forests, 420-1 ,830 m, all major islands.

Although Asplenium macraei is commonly treated as a single endemic species, it is extremely variable in frond size, shape, and dis-section, ranging from 1-pinnate with more or less rectangular and entire pinnae to 2-pin-nate-pinnatifid with finely dissected and triangular pinnae. All other characters, includ-ing those of the rhizomes, scales, venation, ridged stipes, and persistence of old, brown stipes, seem identical. Variants of this taxon are found growing in restricted geographic locations, and although they may remain mor-phologically distinct, there is usually an apparent continuum of intermediates. Whether or not there are clear discontinuities in this diversity needs further study. Several species and varieties have been recognized within what is here being treated as a single endemic species. The species and its variants have been given eighteen names involving two genera, seven species, twelve varieties, three forms, and one subspecies.

Various authors have assigned A. macraei to A. erectum Bory, A. lunulatum Swartz, A. rhizophyllum Kunze, and A. sphenolobium Zenker, species with a wider range of distribution outside Hawai 'i. Asplenium barclay-anum C. C. Adams, limited to Cocos Island in the Pacific Ocean, has been noted as very similar to A. macraei. One variety, described from Rapa Island in the Austral Islands (A. macraei Hook. & Grev. var. rapense E. D. Br. & F. Br.), may be a diminutive variant. These names would be synonymous if it is established that A. macraei is indigenous and not endemic.

On Kaua'i, finely dissected, nearly 3-pinnate plants are growing close to 1-pinnate plants, without intermediates, suggesting that two species are present. In addition, illustrations of spores by Skottsberg ( 1942) show substantial differences in spore morphology among forms of Asplenium macraei, again suggesting the possibility of more than one species.

The number of names seen in the synonymy demonstrates the confusion surrounding this taxon. It needs careful study of type specimens, detailed morphological studies, scanning electron microscopy of spores, iso-zyme and DNA investigations, a review of related or identical species in other parts of the world, common-garden experiments, and expanded collections to clarify its status.

Asplenium macraei is a very polymorphic species (see the description of the pinnae); however, the most common forms are 1-pinnate and have deeply lobed, some-what rectangular pinnae. (Some popula-tions may be 2-to 3-pinnate.) This fern may be recognized by its dark brown, dull-surfaced stipes with thin, greenish ridges on either side of the upper surface. The rare A. peruvianum var. insulare has similar stipes, but it often produces plantlets on its upper stipes and lower rachises, while A. macraei is never proliferous.