Lycopodium inundatum Linnaeus, Sp. Pl. 2: 1102. 1753; Lepidotis inundata (Linnaeus) Opiz; Plananthus inundatus (Linnaeus) P. Beauvois.

Plants of marshes and wetlands. Aerial shoots creeping, 5-20 cm, simple or multiple times dichotomous, 1-2 mm in diam., stem together with leaves 5-8 mm wide. Leaves spirally arranged, sparser on creeping side of stem, dense, ascending, yellowish green, not lustrous, lanceolate to linear, bent, 4-7 × 0.5-1.1 mm, papery, both surfaces glabrous, midrib indistinct, base not narrowed, decurrent, sessile, margin entire, apex acuminate. Peduncles solitary, erect, 3-8 cm tall, together with bracts 4-10 mm wide; bracts dense, linear or linear-lanceolate; strobilus yellowish green, terete, 1-5 cm × 5-7 mm; sporophylls dimorphic, yellowish green, linear-lanceolate and lanceolate, imbricate, 2-5 × 0.5-1.2 mm, papery, margin entire, apex acuminate or blunt. Sporangia enclosed or slightly exposed, subspherical, ca. 0.5 mm in diam., apex acuminate.

Bogs, marshes, swamps; 400-1000 m. Fujian [Japan, Russia; Europe, North America].