This paper deals with the bryophyte floras of Nakanoshima and Suwanosejima Islands in the Tokara Islands, located in the transitional part between the subtropical and the warm-temperate zones of Japan. As the result of a study of about 2000 specimens collected from these two islands, the followings were recognized: 28 families, 41 genera and 82 species of the Musci, 24 families, 37 genera and 68 species of the Hepaticae and 1 family, 3 genera and 3 species of the Anthocerotae. The bryophytes whose distributions in Japan are limited to the regions north of the Tokara Islands are as follows: Brachythecium plumosum var. brevisetum, Ditrichum heteromallum, Fauriella tenuis, Funaria hygrometrica, Micromitrium tenerum, Oncophorus crispifolius, Pseudoleskeopsis zippelii, Racomitrium canescens, Sphagnum cuspidatum, Syrrhopodon japonicus, Weissia controversa; Calypogeia tsukushiensis, Cololejeunea, japonica, Gymnomitrion noguchianum, and Scapania parvitexta. The species that have the northernmost limit of their distributions in the Tokara Islands are Rhacelopodopsis camusii, Rhizogonium spiniforme var. ryukyuense and Kurzia lineariloba. As bryophytes which are generally found in volcanic regions, Campylopodium euphorocladum and Gymnomitrion noguchianum are cited. From these results, we may conclude that the flora of bryophytes in the Tokara Islands is more closely related to the flora of the southern Kyushu than that of the Ryukyu Islands south of Amamiohshima Island.

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New additional localities of Gymnostomiella longinervis Bartr. (Splachnaceae) are reported from Okinawa Isl., Miyagi Isl. and Miyako Isl. of the Ryukyu Archipelago. All are restricted to habitats around human dwellings, such as stone walls and tombs. Frequencies of the main associated plants of the G. longinervis communities are summarized as follows, based on 22 quadrats: Cyanophyta (incl. Scytonema julianum, Tolypothrix sp., Gloeothece sp., etc.) 28 %, Adiantum capillus-veneris 73%, Barbula indica 64%, Pteris ryukyuensis 55% and Youngia japonica 45%. Actual contact between G. longinervis and Scytonema julianum is not clearly shown, even using SEM. An association between these two species has already been observed on juvenile plants of G. longinervis developed from gemmae on wet filter paper in Petri dishes.

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Genetic homogeneity or heterogeneity of moss populations (mats) was studied through isozyme peroxidase patterns in three Plagiomniam species, Haplohymenium longinerve and Fissidens taxifolius. Large-sized mats of three Plagiomnium species showed two or seven different patterns, but those of H. longinerve and F. taxifolius showed only one pattern. These facts show that populations of comparatively large-sized mosses are genetically heterogeneous, and those of comparatively small-sized mosses are genetically homogeneous. For the purpose of application of isozyme patterns to taxonomy, the peroxidase zymograms of nineteen species of Thuidiaceae and nine species of Fissidens were investigated. Before conclusions from these results can be drawn, however, further investigation is necessary.

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The outgrowth of female involucres into vegetative thallus structures in the genus Metzgeria is 1) taxonomically more correlated with the primitive groups and is commonly produced in those 16 species, without sporadic occurrence in other species (it occurs rather uncommonly in northwestern European M. furcata, 2) geographically confined largely to the tropical Andes, 3) apparently correlated, in most cases, to the development of archegonia, calyptra and sporophyte. Such outgrowth was recorded by Stephani earlier in his Species Hepaticarum Vol. 1: very brief descriptons of female involucres of M. acuminata, M. adscendens Steph. (Guiana, Brazil), M. filicina and M. imberbis indicate clearly or at least suggest such structures. In both volumes 1 and 6 there are a few other species with similar descriptions; these apparently refer to only somewhat longer (larger) involucres. The presence of a fine illustration of an outgrown female involucre, associated with a calyptra, was noted in his unpublished Icones, of M. adscendens.

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