2. Polypodium sibiricum Siplivinsky, Novosti Sist. Vyssh. Rast. 11: 329. 1974.
东北水龙骨 dong bei shui long gu
Rhizome wide creeping, 2-3 mm in diam., densely scaly; scales brown, lanceolate, 3-4 mm, margin remotely toothed, apex acuminate. Fronds remote. Stipe straw-colored, 5-8 cm, glabrous. Lamina deeply pinnatifid or pinnatisect, oblong-lanceolate in outline, 10-20 × 3-5 cm, subleathery, yellowish green abaxially, grayish green adaxially, glabrous, apex acuminate or caudate. Segments 12-16 pairs, spreading, narrowly lanceolate, 2-2.5 × 0.5-0.6 cm, usually decurrent to adjacent lobes by narrowly winged rachis, apex obtuse or acute. Veins free, veinlets terminating with hydathode near margin, invisible abaxially, hardly visible adaxially. Sori near margin; sporangia interspersed with 40 or fewer sporangiasters, normally without glandular hairs.
Epiphytic on tree trunks or epilithic. Hebei, Heilongjiang, Jilin, Nei Mongol [Japan, Korea, Mongolia, Russia; North America].
This taxon has traditionally been identified as Polypodium virginianum Linnaeus (Sp. Pl. 2: 1085. 1753), but investigations indicate that P. virginianum is confined to E North America, whereas P. sibiricum ranges from the boreal forests of Canada west into N Japan, across China, and into Siberia (Haufler & Windham, Amer. Fern J. 81: 6-22. 1991; Haufler & Wang, Amer. J. Bot. 78: 624-629. 1991).
Polypodium grandiceps G. Nicholson (Ill. Dict. Gard. 4: 592. 1888), described from Taiwan.
Polypodium griseonigrum Baker (Bull. Misc. Inform. Kew 1895: 55. 1895 ["griseo-nigrum"]), described from Yunnan.
Polypodium lobatum Hudson var. hupehense Pampanini (Nuovo Giorn. Bot. Ital., n.s., 22: 252. 1915), described from Hubei.
Polypodium mathewii Tutcher (J. Linn. Soc., Bot. 37. 68. 1905), described from Shandong.
Polypodium micropteris Baker (Bull. Misc. Inform. Kew 1906: 14. 1906), not C. Christensen (1905), described from Yunnan.
Polypodium muliense Ching ex K. H. Shing (Acta Phytotax. Sin. 31: 573. 1993), described from Sichuan.
Polypodium nervopilosum K. H. Shing (Acta Phytotax. Sin. 31: 573. 1993), described from Sichuan.
Polypodium obtusifrons Hayata (Icon. Pl. Formosan. 4: 250. 1914), described from Taiwan.
Polypodium rosthornii Diels (Bot. Jahrb. Syst. 29(2): 205. 1900), described from China ("Kin-shan").
Polypodium trichophyllum Baker (Bull. Misc. Inform. Kew 1906: 13. 1906), described from Yunnan.