8. Pentagramma Yatskievych, Windham, & E. Wollenweber, Amer. Fern J. 80: 15. 1990.
Silverback fern, goldback fern [Greek penta, five, and gramma, lines (as in written characters), for the pentagonal leaf blades]
Michael D. Windham
Plants on rock or terrestrial. Stems short-creeping, erect or ascending, sometimes branched; scales sharply bicolored with black, hard, central stripe and tan margins, narrowly lanceolate, margins entire. Leaves monomorphic, clustered, 5--40 cm. Petiole chestnut brown to black, rounded or nearly so adaxially, glabrous, farinose, or viscid-glandular, with single vascular bundle. Blade triangular-pentagonal, 1--2-pinnate-pinnatifid proximally, pinnatifid distally, herbaceous to leathery, abaxially usually farinose, farina white or yellow, adaxially glabrous or glandular, dull, not striate; rachis straight. Ultimate segments sessile, adnate to rachis and costae their full width, triangular to lanceolate, margins not recurved to form false indusia. Veins of ultimate segments free, obscure, pinnately branched and divergent distally. False indusia absent. Sporangia borne along veins, containing 64 spores, intermixed with farina-producing glands. Spores tan to brown, distinctly trigonal, coarsely tuberculate, tubercules usually somewhat fused, lacking prominent equatorial flange. Gametophytes glabrous. x = 30.
Species 2 (2 in the flora): North America, nw Mexico.
Until recently, Pentagramma was included in Pityrogramma , based on superficial morphologic similarities between the two groups. Differences in leaf morphology, anatomy of the petioles, spore ornamentation, and presumed basal chromosome numbers suggest that the two genera are not closely related and are best placed in different tribes of the Pteridaceae. Within Pentagramma , species limits are not well understood, and workers have advocated recognition of one to three species, with several additional, morphologically cryptic taxa also indicated (but not named). A detailed examination of infra- and interpopulational variation in the group using modern techniques is needed.
Alt, K. S. and V. Grant. 1960. Cytotaxonomic observations on the goldback fern. Brittonia 12: 153--170. Tryon, R. M. 1962. Taxonomic fern notes. II. Pityrogramma (including Trismeria) and Anogramma. Contr. Gray Herb. 189: 52--76. Yatskievych, G., M. D. Windham, and E. Wollenweber. 1990. A reconsideration of the genus Pityrogramma (Adiantaceae) in western North America. Amer. Fern J. 80: 9--17.