4. Lygodium flexuosum (Linnaeus) Swartz, J. Bot. (Schrader). 1800(2): 106. 1801.
曲轴海金沙 qu zhou hai jin sha
Ophioglossum flexuosum Linnaeus, Sp. Pl. 2: 1063. 1753; Hydroglossum flexuosum (Linnaeus) Willdenow; H. scandens (Linnaeus) Willdenow; Lygodium altum (C. B. Clarke) Alderwerelt; L. flexuosum var. accidens R. C. Y. Chou; L. flexuosum var. alta C. B. Clarke; L. pilosum Desvaux; L. scandens (Linnaeus) Swartz; L. semibipinnatum R. Brown; Odontopteris scandens (Linnaeus) Bernhardi; Ophioglossum scandens Linnaeus; Ramondia flexuosa (Linnaeus) Mirbel; R. scandens (Linnaeus) Mirbel.
Rhizome shortly creeping and densely covered with roots, stipes very close together; apex of rhizome covered with dark brown to nearly black hairs. Juvenile fronds once or twice dichotomous, each branch bearing a single pinna deeply palmately 3-7-lobed, lobes almost equal, base of whole pinna cordate, margins serrate and sometimes crenately lobed. Rachis of scandent fronds narrowly winged, flattened and puberulent on adaxial surface between wings; primary rachis branches up to 3 mm (lower ones longest), dormant apex covered with pale brown hairs; secondary rachis branches pinnate to somewhat bipinnate, narrowly ovate to deltoid in outline, commonly ca. 15 × 8 cm; sterile pinnae of lower branches palmate, often 5-lobed, base strongly cordate; higher secondary branches bearing 3-5 (sometimes up to 7) pinnae on each side and an apical one, apical and lower pinnae asymmetrical or ± lobed at base, lowest of branches with 2 or 3(-6) separate quaternary pinnae at base; sterile pinnae 3-10 cm × 8-15 mm above lobed base, margin serrate, apex subacute, lower pinnae stalked, upper pinnae sessile, lamina rather thin; costae usually with scattered long hairs, less often with dense short hairs, veins often with scattered short hairs on abaxial surface, lamina sometimes similarly hairy; fertile pinnae smaller than sterile pinnae, sorophores 3-5 mm (rarely up to 10 mm), at apices of small triangular lobes; indusia glabrous or with a few hairs like those of abaxial surface of lamina; spores finely evenly verrucose.
Open places, climbing on shrubs, in teak (Tectona grandis) and bamboo forests, not in shaded evergreen forests; near sea level to 1000 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Yunnan [Bhutan, India, S Japan, Malaysia, Nepal, Philippines, Sri Lanka, Thailand, Vietnam; E Australia].
In very dry or exposed places, the veins and lamina of Lygodium flexuosum are often rather copiously hairy.
One of us (Garrison Hanks) notes that differences between Lygodium flexuosum and L. japonicum based on pinnule size are problematic, but the taxa are difficult to distinguish in many collections.