Polygala reinii Franch. et Sav. is a perennial herb endemic to the Kinki and Tokai districts of Japan.　To clarify the habitat traits of P. reinii, we surveyed the distribution area of this species and compared the environmental conditions, stand structure, life-form spectra, and floristic composition between the habitats and the non-habitats in secondary Pinus densiflora-Quercus serrata forests of the southeastern parts of the Hyogo Prefecture. Additionally, we examined the relationship between the environmental conditions and the density of P. reinii individuals within the study area and assessed the variation in climatic conditions and habitats in the entire geographical distribution range of P. reinii by inspecting their specimens stored in several herbaria.　The results of the field survey showed that P. reinii was found mostly on the crest slopes along ridge lines.　In the habitats, the organic layer was thinner, the electric conductivity of surface soil was lower, and the soil hardness was greater, compared to those in the non-habitats.　Evergreen broad-leaved trees were commonly dominant in the understory of both, the habitats and the non-habitats.　Meanwhile, deciduous broad-leaved trees were more abundant in the understory of the habitats than in that of the non-habitats.　Life-form spectra and floristic composition were characterized by a higher proportion of perennial herbs, including forest edge species and grassland species.　The density of the P. reinii individuals was positively correlated with overstory opening and soil hardness while being negatively correlated with the thickness of the organic layer.　These results suggested that the undeveloped forests such as open forests are suitable habitats for the growth and establishment of P. reinii. This was also supported by the habitat records found on the labels of several specimens of this species.　Selective cutting of inhibitors such as the evergreen broad-leaved trees is thus considered to be necessary for the conservation of P. reinii.　This is especially important in the stands where they are growing dominant with the progression of vegetation succession after the cessation of traditional management．

Rheophytes are plants that grow on the banks and rocks along mountain streams where they are frequently inundated by floods after high precipitation events.　The development of rheophytic communities is considered to be related to inundation frequency.　However, the estimation of inundation frequency in the field is difficult. Relative elevation of the vegetation stand from the ordinary water level does not necessarily indicate the inundation frequency even along the same stream.　Therefore, we devised the “rheophytic zone template,” which shows the range of the rheophytic zone by the relationship between the catchment area and the cross-sectional area of flow.　In this study, we attempted to explain the ecological distribution of herbaceous rheophytic communities along the mountain streams in Iriomote Island, by using the rheophytic zone template.　From 277 surveyed vegetation stands, three communities were classified and identified into the following associations: Lindsaeo japonicae-Salvietum pygmaeae, Pileo-Arundetum formosae, and Argostemmo-Begonietum formosanae. Mean percentage of rheophytes per stand reached almost half of the component species in Lindsaeo japonicae-Salvietum pygmaeae, and 20% in Pileo-Arundetum formosae.　These two associations were distributed within the rheophytic zone defined using the rheophytic zone template, with the former association occurring in sites where flooding was more frequent than that in the other sites in the zone.　On the other hand, Argostemmo-Begonietum formosanae, in which the percentage of rheophytes was only 9%, was not regarded as a rheophytic community, because its distribution was above the rheophytic zone.　These results revealed that flood disturbance was the main factor responsible for the ecological distribution of the rheophytic communities by preventing invasion of non-rheophytic plants.　Furthermore, our results suggested that artificial alteration of mountain streams that change the frequency and magnitude of natural flood disturbance could cause degradation of vulnerable rheophytic communities.

Distribution and habitat of Albizia julibrissin var. glabrior（Koidz.） H. Ohashi and A. kalkora （Roxb.） Prain were studied.　Two new localities of these species were found, respectively.　Albizia julibrissin var. glabrior endemic to Japan is distributed from the middle- and northern Ryukyu Islands through western Kyushu to the Tsushima Islands.　It shows the northbound distribution in western Kyushu.　Albizia kalkora which is widely distributed in Southeastern Asia shows disjunct distribution in Japan, namely in Amami-Ohshima, Tokara Islands, northwestern Miyazaki Prefecture, Goto Islands and southwestern Korea.　Distribution maps of these species were illustrated.　These species are usually found in ruderal sites such as slope on road side.　The communities which are composed with these species are phytosociologically belonging to Alliance Clerodendro-Mallotion japonicae, Order Fico-Mallotetalia.