6. Astrolepis D. M. Benham & Windham, Amer. Fern J. 82: 55. 1992.
Star-scaled cloak ferns [Greek astro, star, and lepis, scale, in reference to the starlike scales on the adaxial blade surface]
Dale M. Benham
Michael D. Windham
Plants usually on rock. Stems compact to short-creeping, erect to ascending, sparingly branched; scales tan to chestnut brown, concolored to weakly bicolored, linear-attenuate, margins ciliate-dentate to entire. Leaves monomorphic, densely clustered, 7--130 cm. Petiole dull chestnut brown or straw-colored, rounded adaxially, sparsely to densely covered with scales, with 2 vascular bundles. Blade linear to linear-oblong, 1-pinnate to pinnate-pinnatifid, leathery, abaxially covered with overlapping, lanceolate to ovate, ciliate scales with underlying layer of stellate scales, adaxially sparsely to densely covered with stellate or coarsely ciliate scales, often glabrescent when mature, dull, not striate; rachis straight. Ultimate segments (pinnae) stalked to subsessile, free from axis, ovate, oblong or elongate-deltate, cordate to subcordate or rarely truncate at base, usually more than 4 mm wide; segment margins plane, undifferentiated, not recurved to form false indusia. Veins of ultimate segments obscure, pinnately branched and divergent distally. False indusium absent. Sporangia scattered along veins near pinna margins (often clustered near notches between pinna lobes), containing 32 or 64 spores, not intermixed with farina-producing glands. Spores light to dark brown, tetrahedral-globose, rugose, lacking prominent equatorial ridge. Gametophytes glabrous. x = 29.
Species ca. 8 (4 in the flora): North America, Mexico, West Indies, Central America, South America.
The species of Astrolepis have traditionally been assigned to either Notholaena (R. M. Tryon 1956) or Cheilanthes (J. T. Mickel 1979b; R. M. Tryon and A. F. Tryon 1982). Recent biosystematic analyses by D. M. Benham and M. D. Windham (1992) indicate, however, that the star-scaled cloak ferns form a distinctive, monophyletic group worthy of generic recognition. The combination of a chromosome base number of x = 29, pinnate leaves, two vascular bundles in the petioles, unique stellate or coarsely ciliate scales on the adaxial blade surface, and other characteristics separate Astrolepis from related genera.
Benham, D. M. 1989. A Biosystematic Revision of the Fern Genus Astrolepis (Adiantaceae). Ph.D. dissertation. Northern Arizona University. Benham, D. M. 1992. Additional combinations in Astrolepis. Amer. Fern J. 82: 59--62. Benham, D. M. and M. D. Windham. 1992. Generic affinities of the star-scaled cloak ferns. Amer. Fern J. 82: 47--58. Hevly, R. H. 1965. Studies of the sinuous cloak fern (Notholaena sinuata) complex. J. Arizona Acad. Sci. 3: 205--208. Tryon, R. M. 1956. A revision of the American species of Notholaena. Contr. Gray Herb. 179: 1--106.