Chlamydomonas is a unicellular volvocalean genus with two equal flagella and single or multiple pyrenoids in the chloroplast. In this study, culture strains originating from two localities in Japan were identified as Chlamydomonas (Cd.) perpusilla (Korshikov) Gerloff var. perpusilla and Cd. pumilio H. Ettl var. pumilio based on light microscopy. Neither species has been previously recorded in Japan. Molecular phylogenetic analyses based on 18S ribosomal RNA genes showed that Cd. perpusilla is closely related to Chlorogonium, and Cd. pumilio formed a clade with some Chlamydomonas species and Polytoma.

The morphology of utricles was critically studied in order to elucidate the species composition of prostrate Codium in Japan. Utricle morphology, such as length, diameter, shape of apical portions, presence or absence of hairs (or hair-scars) and alveolate ornamentation, are shown to characterize the clades recognized in our previous molecular analysis. These molecular and morphological congruences indicate that these morphological features reflect the phylogeny of Codium. The prostrate Codium in Japan was classified into the following five species: C. arabicum Ktzing, C. capitulatum Silva & Womersley, C. dimorphum Svedelius, C. hubbsii Dawson, C. lucasii Setchell.

The genus Ulva in Hokkaido, Japan was investigated using a molecular phylogenetic technique based on nuclear encoded ITS2 (Internal Transcribed Spacer 2) sequences and morphological observations of ten species, including two unidentified species detected from 78 samples growing in this area. Six samples of U. prolifera O. F. Mller distributed in the estuary of the Nobusha River and Furubira River possessed an identical sequence of the ITS2 region with U. procera (K. Ahlner) Hayden & al. from its type locality, Sweden. Unidentified species 1 (Ulva sp. 1) had distinctive morphological characteristics such as a large crescent blade. Unidentified species 2 (Ulva sp. 2) was not discriminated from U. compressa L. by morphology.

Chromosome numbers of Myosoton aquaticum were counted for 44 plants from 37 areas in Japan. All M. aquaticum plants examined showed a 2n = 28 chromosomal count. The metaphase chromosomes ranged from 1.3 to 2.9 m in length and 1.2 to 2.5 in arm ratio. On the basis of the nomenclature proposed by Levan et al. (1964), the 28 chromosomes were divided into 14 metacentric chromosomes and 14 submetacentric chromosomes, with the chromosome complement formulated as 2n = 28 = 14m+14sm.

A new species of Lespedeza (Leguminosae: Papilionoideae) from China and Japan is described as L. lichiyuniae T. Nemoto, H. Ohashi & T. Itoh. This new species is attributed to subgenus Lespedeza because of the presence of cleistogamous flowers and fruits. The species is similar to L. cuneata and L. juncea, but differs from them in having pink or pale purple flowers, under surface of leaflets densely covered with longer sericeous hairs and cleistogamous pods relatively longer than calyx and densely pubescent. The species occurs mainly in inland provinces of central China, but is distributed also in coastal China and in Japan. Plants of the species in Japan are presumed to have been imported from China as a mixture of roadside cover plants together with Lespedeza caraganae, L. davidii, L. davurica, L. floribunda and L. inschanica.

A new species, Arabidopsis umezawana Kadota, is here described from Rishiri Island, Hokkaido, northern Japan. Arabidopsis umezawana is distinguished from A. kamchatica subsp. kamchatica by having plantlets at axils and inflorescences, uneven, adaxial surface of cauline leaves, suborbicular seeds with wings ca. 0.3 mm wide, non-nerved valves and the absence of radical leaves at anthesis; from A. halleri subsp. gemmifera by having annual or biennial habit, suborbicular, winged seeds and the absence of radical leaves at anthesis. This new species is restricted to the alpine zone of Mt. Rishirizan and grows under Betula ermanii - Alnus maximowiczii scrub and in alpine meadow. A new combination, Arabidopsis gemmifera, is also propsed.

As part of a series of studies on the typification of botanical names published by Tomitaro Makino, proposals for the lectotypification, neotypification and the verification of other type materials for taxa in the Gentianaceae are presented here.