A Biosystematic Study of Nipponolejeunea Hatt. (Hepaticae)

The genus Nipponolejeunea Hattori was established by Hattori (1944) based on Pycnolejemea pilifera Steph. from Japan. Its primary important generic characters include 1) the two gynoecial innovations, 2) the triplicate perianth, and 3) the long cilia on leaf- and underleaf-margin. Hattori (1944) also assigned Pycnolejeunea subalpina Horik. to Nipponolejeunea, thus admitting two Japanese species in that genus. Since then, the genus Nipponolejeunea has been repeatedly discussed, especially by Mizutani (1961) and Schuster (1963) from taxonomic points of view. The branching and innovation types of Nipponolejeunea were described by Mizutani (1970); Inoue (1976) proposed the subgeneric separation of the two species, as subgen. Nipponolejeunea (with N. pilifera) and subgen. Mizutania (with N. subalpina). Surprisingly, Grolle (1981) recently found a fossil species of this genus in Europe, N. europaea Grolle, embedded in an amber, from the southern part of Scandinavia. The species belongs in the subgen. Mizutania and, according to Grolle (1981), might even prove to be conspecific with N. subalpina. Regarding the taxonomic position of Nipponolejeunea, Mizutani (1961) placed the genus in the subfamily Jubuloideae together with Jubula and Neohattoria, but Schuster (1963) proposed an independent subfamily in the Lejeuneaceae for this genus, Nipponolejeuneoideae Schust. & Kachroo, which has now become generally accepted (cf. Gragstein, 1979; Schuster, 1979).