A new species of Frullania, F. pseudoalstonii Tsudo et J. Haseg. is described from Miyazaki, southern Japan. The species belongs to the subgenus Frullania and characterized by caducous leaves and leaf-lobes with scattered ocelli in addition to moniliate ones. Frullania alstonii Verd. known from Southeast Asia is closely related to this new species, but differs in distant, smaller underleaves, noncaducous leaves, and leaf-lobules conspicuously inclined to the stem. Two Japanese species of the subgenus Frullania, F. densiloba Steph. ex Evans and F. aoshimensis Horik. also resemble the present new species in having moniliate ocelli, but differ in lacking scattered ocelli and noncaducous leaves.

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Riccia cavernosa Hoffm. is newly found in Japan. Description and illustration of this species are given based on Japanese material.

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Although circadian rhythms of various processes have been observed in higher plants, few examples have been examined in relatively primitive land plants such as pteridophytes and bryophytes. Recently, the author's group observed circadian expression of the PpLhcb2 gene, which encodes a light-harvesting chlorophyll a/b-binding protein, in the moss Physcomitrella patens. Analyses of this rhythm suggest that the regulatory mechanism of the circadian clock of P. patens may be at least partly different from that of higher plants. In this short essay, the author briefly summarizes current studies on the mechanism of the circadian clock in Arabidopsis thaliana, and on circadian rhythms of primitive plant species. In particular, the essay will focus on recent observations by the author's group about circadian clock-related genes in P. patens, and discuss the possibility that P. patens could be a useful model for studies on the molecular mechanisms of the circadian clock.

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