Description from Flora of China
Lycopodium serratum Thunberg in Murray, Syst. Veg., ed. 14, 944. May-Jun 1784; Huperzia myriophyllifolia (Hayata) Holub ["myriophylla"]; H. selago (Linnaeus) Bernhardi ex Schrank & Martius var. serrata (Thunberg) Á. Löve & D. Löve; H. serrata f. intermedia (Nakai) Ching; H. serrata f. longipetiolata (Spring) Ching; H. serrata var. longipetiolata (Spring) H. M. Chang; L. javanicum Swartz; L. serratum var. intermedium Nakai; L. serratum var. javanicum (Swartz) Makino; L. serratum var. longipetiolatum Spring ["longe-petiolatum"]; L. serratum var. myriophyllifolium Hayata; L. serratum var. thunbergii Makino; Urostachys myriophyllifolius (Hayata) Herter ["myriophyllus"]; U. serratus (Thunberg) Herter ex Nessel.
Plants terrestrial. Stem erect or ascending, 10-30 cm, 1.5-3.5 mm in diam. at middle, together with leaves 1.5-4 cm wide, 2-4 times dichotomously branched, upper portion often with bulbils. Leaves sparse, attached at right angles with stem, lustrous, narrowly elliptic, conspicuously contracted toward base, straight, 1-3 cm × 1-8 mm, thinly leathery, both surfaces glabrous, midrib conspicuously raised, base cuneate, decurrent, petiolate, margin straight and not crispate, irregularly toothed, apex acute or acuminate; teeth acute at apex, coarse or slightly small. Sporophylls homomorphic with trophophylls; sporangia visible on both sides of sporophylls, yellowish, reniform.
Although there are DNA data (Ji et al., J. Syst. Evol. 46: 213-219. 2008) showing that there is strong intraspecific variation at the molecular level, morphological differences at the intraspecific level are not well understood. More studies are needed.
The most distinguishing character of Huperzia serrata is its leaf margins with coarse teeth.
Forests, shrubs, roadsides; 300-2700 m. Throughout China except parts of N and NW China [Bhutan, Cambodia, India, Indonesia, Japan, Korea, Laos, Malaysia, Myanmar, Nepal, Philippines, Russia, Sri Lanka, Thailand, Vietnam; Australia, Central America, Pacific islands].