Plants terrestrial or epilithic, evergreen or seasonally green, erect, 10-45 cm, without creeping rhizomes or stolons, without elongate tuber at base of stem. Rhizophores at intervals throughout length of creeping stem and branches and to upper part of main stem, borne on ventral side in axils of branches. Main stems branched from lower part upward, pinnately branched, stramineous, subquadrangular, sulcate, glabrous; primary leafy branches 3-10 pairs, 2 or 3 times pinnately branched; secondary branches once or twice pinnately branched, regularly long; adjacent primary branches on main stem 2-4 cm apart; leafy portion of main stem including leaves 0.4-0.7 mm wide at middle, ultimate branches 3.3-6 mm wide including leaves. Axillary leaves on main stems larger than those on branches, ovate, ovate-triangular, or ovate-elliptic, base not peltate, obtuse; axillary leaves on branches symmetrical, ovate-triangular or ovate, 2-3.5 × 1.2-2.8 mm, base exauriculate, margin ciliolate. Dorsal leaves asymmetrical, those on main stems slightly larger than those on branches; dorsal leaves on branches approximate or contiguous, obliquely ovate-elliptic, 1.5-3.2 × 0.6-1 mm, carinate, base subcordate or cuneate, not peltate, margin ciliolate, apex aristate, arista curved, 0.8-1.6 mm. Ventral leaves asymmetrical, those on main stem larger than those on branches; ventral leaves on branches distant or approximate, spreading, oblong or oblong-ovate, 2.2-5 × 1-2.2 mm, margin denticulate, apex subacute; basiscopic base decurrent, margin ciliolate at base (elsewhere subentire); acroscopic base enlarged, broader, strongly overlapping stem and branches, margin ciliolate in basal half (denticulate to apex). Strobili solitary, terminal, compact, dorsiventrally complanate, 6-12 × 1.5-3 mm; sporophylls unlike sterile leaves, strongly dimorphic, resupinate, not white-margined; dorsal sporophylls oblong-lanceolate, sharply carinate, margin ciliolate, apex acute or acuminate, with sporophyll-pteryx complete and sparsely shortly ciliolate; ventral sporophylls ovate-triangular, carinate, margin shortly ciliolate; megasporophylls in basal portion on lower side of strobilus; microsporangia orbicular, rather thin, cells uniform; microspores pale yellow, megaspores white-yellow.
Selaginella effusa is similar to S. heterostachys but differs in the axillary leaves ciliolate and ovate-triangular.
Guangdong, Guangxi, Guizhou, Xizang, Yunnan [Vietnam].
On rocks in shaded places, terrestrial along roadsides in forests; 200-1500 m.