Polypodium sibiricum Sipliv.

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.