8. Lycopodium cernuum Linnaeus, Sp. Pl. 2: 1103. 1753.
垂穗石松 chui sui shi song
Lepidotis cernua (Linnaeus) P. Beauvois; Lycopodiella cernua (Linnaeus) Pichi Sermolli; Lycopodium cernuum f. sikkimense (Müller (Halle)) H. S. Kung; L. cernuum var. sikkimense (Müller (Halle)) C. B. Clarke; L. sikkimense Müller (Halle); Palhinhaea cernua (Linnaeus) Vasconcellos & Franco; P. cernua f. sikkimensis (Müller (Halle)) H. S. Kung; P. cernua var. sikkimensis (Müller (Halle)) Ching; P. lufengensis C. Y. Yang.
Plants medium-sized to large; aerial shoots erect, up to 60 cm tall, terete, 1.5-2.5 mm in diam. at middle, glabrous, dichotomously branched with well-differentiated lateral branchlets much branched; leaves of aerial shoots spirally arranged, sparse, subulate to linear, ca. 4 × 0.3 mm, straight or slightly involute, papery, midrib indistinct, base rounded, decurrent, sessile, margin entire, apex acuminate. Lateral branches ascending, dichotomously branched with well-differentiated lateral branchlets much branched, pubescent or glabrous; leaves of lateral branches and branchlets spirally arranged, dense, slightly bent upward, subulate to linear, 3-5 × ca. 0.4 mm, papery, longitudinally furrowed on surface, glabrous, midrib indistinct, base decurrent, sessile, margin entire, apex acuminate. Strobilus solitary, terminal on small branches, often pendulous when mature, pale yellow, shortly terete, 3-10 × 2-2.5 mm, sessile; sporophyll ovate-rhombic, imbricate, ca. 0.6 × 0.8 mm, margin membranous, with irregular teeth, apex acute, caudate. Sporangia enclosed.
Forests, forest margins, shaded places in shrubs or beside rocks; 100-2300(-2800?) m. Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [tropical and subtropical areas of Asia, Central and South America, Pacific islands].
Branches of this species are hairy or glabrous; if hairy then the quantity of hairs is variable. This species can be divided into two forms based on indumentum: Lycopodium cernuum f. cernuum (branches without hairs) and L. cernuum f. sikkimense (branches with hairs). Lycopodium cernuum f. sikkimense has a more southern distribution than the typical form. In Sichuan, the typical form is more common, while this form is more common in Yunnan.
A form with ciliate sterile leaves is recognized as Palhinhaea cernua f. ciliatomarginata W. M. Chu (Fl. Yunnan. 20: 30. 2006).