Polypode de Sibérie

Stems often whitish pruinose, slender, to 6 mm diam., acrid-tasting; scales concolored to weakly bicolored, uniformly dark brown, often lighter near base, lanceolate, contorted distally, margins denticulate. Leaves to 25 cm. Petiole slender, to 1 mm diam. Blade oblong-linear, pinnatifid, usually widest at or near middle, to 4 cm wide, somewhat leathery; rachis sparsely scaly to glabrescent abaxially, glabrous adaxially; scales lanceolate-ovate, usually more than 6 cells wide. Segments oblong, less than 7 mm wide; margins entire to crenulate; apex rounded to broadly acute; midrib glabrous adaxially. Venation free. Sori midway between margin and midrib to nearly marginal, less than 3 mm diam., circular when immature. Sporangiasters present, less than 40 per sorus, heads normally without glandular hairs. Spores less than 52 µm, tuberculate with tubercles, surface projections more than 3 µm tall. 2 n = 74.

Sporulating summer--early fall. Cracks and ledges on rock outcrops; on a variety of substrates including granite and dolomite; 100--1000 m; Greenland; Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon; Alaska; n Asia.

This boreal diploid has traditionally been identified as Polypodium virginianum (T. M. C. Taylor 1970; F. A. Lang 1971), but recent investigations indicate that it is conspecific with the eastern Eurasian species P . sibiricum (C. H. Haufler and M. D. Windham 1991). The sporangiasters of P . sibiricum normally lack glands, but some collections have sporangiasters with a few glandular hairs. Although such collections could be misidentified, the spores of P . sibiricum are less than 52 µm and clearly distinguish it from P . virginianum , P . amorphum , and P . saximontanum . Hybridization occurs between P . sibiricum and P . virginianum where these species overlap in Canada, forming triploid individuals with misshapen spores (C. H. Haufler and Wang Z. R. 1991).