7. Polypodium appalachianum Haufler & Windham, Amer. Fern J. 81: 18. 1991.
Appalachian polypody, polypode des Appalaches
Stems often whitish pruinose, slender, to 6 mm diam., acrid-tasting; scales concolored to weakly bicolored, uniformly golden brown or slightly darker near apex, lanceolate, contorted distally, margins denticulate. Leaves to 40 cm. Petiole slender, ± 1.5 mm diam. Blade elongate-deltate, rarely oblong, pinnatifid, usually widest at or near base, to 9 cm wide, herbaceous to somewhat leathery; rachis sparsely scaly to glabrescent abaxially, glabrous adaxially; scales lanceolate-ovate, usually more than 6 cells wide. Segments linear to oblong, less than 8 mm wide, margins entire to crenulate; apex acute to narrowly rounded; midrib glabrous adaxially. Venation free. Sori midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature. Sporangiasters present, usually more than 40 per sorus, heads densely covered with glandular hairs. Spores less than 52 µm, verrucose, projections less than 3 µm tall. 2 n = 74.
Sporulating summer--fall. Cliffs and rocky slopes; on a variety of substrates; 0--1800 m; N.B., Nfld., N.S., Ont., P.E.I., Que.; Ala., Conn., Del., D.C., Ga., Ky., Maine, Md., Mass., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va.
Polypodium appalachianum is a newly recognized species traditionally identified as the diploid cytotype of P . virginianum (A. M. Evans 1971; I. Manton and M. Shivas 1953). Because the tetraploid cytotype is an allopolyploid (C. H. Haufler and Wang Z. R. 1991), and the type specimen of P . virginianum is tetraploid (R. Cranfill and D. M. Britton 1983), the diploid is recognized here as a distinct species, P . appalachianum . Some collections of P . appalachianum can be difficult to distinguish from P . virginianum , but the latter species has spores averaging more than 52 µm, and P . appalachianum has spores less than 52 µm. Frequent hybridization between P . appalachianum and P . virginianum forms morphologically intermediate, triploid individuals with misshapen spores. Particularly confusing is the frequent occurrence of the triploid sympatric with only one parent or with neither parent nearby.