Description from Flora of China
Lycopodium obscurum var. japonicum Thunberg.
Stolons subterranean, slender and creeping, brownish yellow, glabrous or with few leaves; lateral branches erect, 18-50 cm tall, lower part not branched, distal part forked; branches dense, slightly complanate, whole branches forming a flabellate, semi-orbicular, or terete shape. Leaves spirally arranged, slightly sparse, ascending or nearly spreading, linear-lanceolate, 3-4 × ca. 0.6 mm, leathery, midrib slightly conspicuous, base cuneate, decurrent, sessile, margin entire, apex acuminate, with short acute tip. Strobili solitary, terminal on branchlets, erect, terete, sessile, 2-3 cm × 4-5 mm; sporophylls broadly ovate, ca. 3 × 2 mm, papery, margin membranous, with erose teeth, apex acute. Sporangia borne in axils of sporophylls, enclosed.
Stone crevices or moss layer in canopy gaps of Betula, Larix, Picea, and Pinus forests. Heilongjiang, Jilin, Liaoning [Japan, Korea, Russia; North America].