地耳蕨 di er jue

Ophioglossum zeilanicum Houttuyn, Nat. Hist. 14: 43. 1783; Acrostichum quercifolium Retzius; Gymnopteris quercifolia (Retzius) Bernhardi; Leptochilus zeilanicus (Houttuyn) C. Christensen; Quercifilix zeilanica (Houttuyn) Copeland.

Plants terrestrial, 10-20 cm tall. Rhizome ascending to long creeping, slender, 2-3 mm in diam., densely scaly; scales brown, glossy, lanceolate, ca. 3 mm, membranous, margins ciliate, apices fibriform. Fronds distant, interval 5-10 mm, obviously dimorphic; sterile fronds usually in rosette, not erect; stipe dark stramineous, 3-8 cm, slender, ca. 1.5 mm in diam. at base, grooved above, densely scaly at base; densely hairy throughout with long brown articulate hairs. Lamina green, triangular-ovate, 6-9 × 2.5-3.5 cm, herbaceous, hairy abaxially and along margins, base cordate to hastate, apex obtuse, undulate, trifoliate to pinnatifid, usually with 1 pair of separate pinnae; rachises and costae stramineous, hairy; costae and main veins stramineous, glabrous adaxially, hairy abaxially; lateral pinnae opposite, applanate, subsessile or shortly stalked, triangular, 1-2.5 × 1-2 cm, bases rounded cuneate to subcordate, asymmetrical, apices rounded, margins subentire or slightly undulate, sometimes bearing auricles basiscopically at base; terminal pinna oblong, base broadly cuneate, apex rounded, lobed at margins to 1/3 toward costa, lobes rounded-subdeltoid, entire. Fertile fronds erect; stipe slender, 20-25 cm, very sparsely scaly or glabrescent; lamina trifoliate, very contracted; terminal pinna linear, 50-70 × 2-3 mm, stalk ca. 1 cm, base cuneate, apex obtuse, margins undulate or lobed; lateral pinnae opposite, oblique, shortly stalked, linear, 10-20 × 2-3 mm, bases bearing short lobe basiscopically, apices obtuse, margins undulate. Veins anastomosing, forming copious areoles, with or without included veinlets, these simple or forked. Sori orbicular, anastomosing in line, throughout abaxial surface when mature, exindusiate.

On muddy rocks in forests, near streams, on steep banks; 100-1000 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Taiwan, Yunnan [S India, Indonesia, Laos, Malaysia, Philippines, Sri Lanka, Thailand, Vietnam; Indian Ocean islands (Mauritius), Pacific islands (Polynesia)].

The unusual spelling "zeilanica" is published as such and is to be maintained. It should not be corrected into the more common "zeylanica" or "ceylanica." Tectaria zeilanica was previously most commonly treated as the separate monotypic genus Quercifilix, but molecular evidence shows that this genus is embedded within the greater Tectaria clade. The species is easily recognized by its small size, its coarsely crenate sterile leaves (that somewhat resemble those of Quercus, hence the name), and its trifoliate, strongly contracted fertile leaves, with anastomosing sori that cover the entire lower side of the lamina when mature.