Lycopodium sieboldii Miquel, Ann. Mus. Bot. Lugduno-Batavi 3: 184. 1867; Huperzia sieboldii (Miquel) Holub; Urostachys sieboldii (Miquel) Herter ex Nessel.

Lycophytes, medium-sized. Stems caespitose, mature branches pendulous, 1 to several times forked, 30-45 cm, stem together with leaves cordlike, 2-5 mm wide at middle. Leaves twisted and forming 2 rows. Trophophylls dense, adnate to branches, slightly incurved, lustrous, elliptic, less than 5 mm, ca. 3 mm wide, midrib indistinct, hard, raised abaxially, base cuneate, decurrent, sessile, margin entire, apex subacute. Strobili terminal on branches, 1.5-2.5 mm in diam. Sporophylls ovate, midrib indistinct, base cuneate, margin entire, apex blunt without mucro. Sporangia visible from outside of sporophylls, yellowish, reniform, vertically bisected.

Phlegmariurus sieboldii has elliptic trophophylls and apically blunt sporophylls.

Epiphytic on tree trunks in forests; 400-1400 m. Taiwan [Japan, Korea].