对开蕨 dui kai jue

Phyllitis japonica Komarov, Izv. Bot. Sada Akad. Nauk SSSR 30: 192. 1932; Asplenium scolopendrium Linnaeus subsp. japonicum (Komarov) Rasbach, Reichstein & Viane.

Plants up to ca. 60 cm tall. Rhizome erect or ascending; scales brown, thin, narrowly triangular to triangular, entire. Fronds caespitose; stipe brown, 10-20 cm, with sparse scales; lamina narrowly oblong, 15-45 × 3.5-4.5(-6) cm, leathery, base cordate, margin entire or slightly sinuate, apex acute. Midrib (rachis) distinct, brown basally and becoming green toward apex, raised and rounded on both sides, with small scales at base; lateral veins obscure, anadromous but running straight and almost parallel. Frond green and fleshy when fresh, after drying leathery and brownish green, abaxially subglabrous. Sori linear, usually 7-25 mm, on neighboring veinlets and opposite; indusia brown, linear, entire, opening toward each other (scolopendrioid), persistent. Spores with lophate (alate) perispore, average exospore length 31-35 µm. Plants sexual tetraploid: 2n = 144.

Terrestrial; 700-1000(-2600 in Taiwan) m. Jilin (Changbai, Fusong, Ji’an), Taiwan [Japan, Korea, SE Russia; North America].

Due to the peculiar frond shape and double sori facing each other, both Asplenium komarovii and A. scolopendrium were often placed in the former satellite genus Phyllitis. Modern studies confirm that it deserves no recognition. The group consists of two species: a diploid ancestral taxon (2n = 72) essentially in Europe and an autotetraploid in North America (including Mexico) and NE Asia (Mitui, J. Jap. Bot. 41: 60-64. 1966; Sci. Rep. Tokyo Kyoiku Daigaku, B, 13: 285-333. 1968).

Asplenium komarovii originated by chromosome doubling in diploid A. scolopendrium; in local floras it is usually mentioned under this latter name. In the absence of a chromosome count or flow cytometric data, it can best be distinguished from its ancestor by its larger mean exospore length (more than 31 µm).