Circumscription of three sections of Hemerocallis that were recognized by Matsuoka & Hotta (Acta Phytotax. Geobot. 22: 25–43, 1966) and Hotta (Fl. Jap. IVb: 130–134, 2016) was evaluated through MIG-seq analysis of 45 samples of seven species and nine varieties of Hemerocallis, covering all taxa native to Japan except H. fulva vars. aurantiaca and pauciflora. The Neighbor-Net network of the MIG-seq data yielded three major clusters corresponding to the three sections of Hemerocallis recognized by Matsuoka & Hotta (1966) and Hotta (2016), except that H. hakuunensis and H. major, which were included in H. sect. Fulvae by Matsuoka & Hotta (1966) and Hotta (2016), were embedded in the cluster of H. sect. Hemerocallis. Hemerocallis hakuunensis and H. major usually have fragrant flowers and lack horizontally spreading rhizomes in the same manner as H. sect. Hemerocallis, which are not features of H. sect. Fulvae. We propose a transfer of H. hakuunensis and H. major from H. sect. Fulvae to H. sect. Hemerocallis. Hemerocallis minor appears to be conspecific with H. lilioasphodelus and is better regarded as H. lilioasphodelus var. minor. Hemerocallis lilioasphodelus var. thunbergii is placed in synonym under H. lilioasphodelus var. lilioasphodelus.

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Asplenium serratipinnae (Aspleniaceae: Polypodiales), an allotetraploid species between the diploid race of A. normale and A. oligophlebium is described as new. It is endemic to Japan and morphologically most similar to A. normale, but differs in having narrower pinnae with an auriculate to hastate acroscopic base and deeply serrated margins.

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Phenological responses in species of Cardamine are often accompanied by morphological changes that result in disagreement among researchers about the taxonomic rank and status of a particular taxon. The gross morphology of two closely related eastern Asian species, Cardamine fallax (O. E. Schulz) Nakai and C. occulta Hornem., was compared by growing plants under controlled photoperiod and vernalization conditions. Response to photoperiod and vernalization in C. fallax and C. occulta explained differences in phenology between the two species under natural conditions. The gross morphology was distinctive between the two species grown under the same conditions, but overlapped when C. fallax was grown in the spring photoperiod-temperature regime and C. occulta grown in the autumn environmental regime. Cardamine fallax is distinct from C. occulta in gross morphology when seasonality in flowering time is taken into account. The findings support the distinction between C. fallax and C. occulta. A survey of herbarium specimens revealed the upper cauline leaves of C. fallax to be moderately or densely hairy, while those of C. occulta were glabrous or sparsely hairy.

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Potamogeton ×angustifolius (P. gramineus × P. lucens) was newly recorded in Japan from a pond in Tsugaru-shi, Aomori Prefecture. The hybrid nothospecies was identified based on morphological observations and measurements, molecular analyses using cloned nuclear adhA gene and chloroplast rpl20–rps12 intergenic spacer, and pollen viability. The putative hybrid had morphological traits intermediate between P. gramineus and P. lucens, nuclear haplotypes matching those of the two parental lineages, and lower pollen viability than P. lucens (not compared with P. gramineus). The maternal lineage of the hybrid was presumed to be P. gramineus, based on chloroplast sequences. The hybrid characteristically shows well-branched stems in the upper part of shoots, as in P. gramineus, and both clearly petiolate and sessile submerged leaves with distinctive netted venation. Similar plants were collected in the 1980s from a ditch near the pond, suggesting that the hybrid may have been present for more than 30 years in this area.

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Salvia lutescens (Koidz.) Koidz. var. intermedia (Makino) Murata (Lamiaceae) has been proved to be divided into two allopatric taxa, one in the Kinki Distr. ("Kinki form") and the other in the Kanto Distr. ("Kanto form") according to the recent molecular phylogenetic and morphological analyses. In this sense, the past lectotypification of var. intermedia by Murata & Yamazaki (1993) was incorrectly applied, as the lectotype (N. Takemura s.n., MAK), belonging to the Kinki form, is in serious conflict with the protologue of Makino (1901) which agrees well with the Kanto form. Therefore, I revise the lectotypification of var. intermedia in accordance with ICN Art. 9.19(b) to change into a specimen of the Kanto form (R. Yatabe & J. Matsumura s.n., TI), and describe the Kinki form as a new variety, var. occidentalis. Furthermore, lectotype of S. lutescens var. crenata is also designated. A key to the varieties and taxonomic treatment of each taxon of S. lutescens is provided.

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Najas minor and N. oguraensis (Hydrocharitaceae) are annual submerged plants and are difficult to distinguish owing to their similarities. While the number of anther locules and the size of the leaf epidermal cells differ between the two species, the anther locules are often difficult to observe on herbarium specimens and the effectiveness of using the size of the leaf epidermal cells as a taxonomic key character is currently unknown. We examined the size of the leaf epidermal cells in living plants and in dried specimens to evaluate the effectiveness of this feature in species identification. We first identified the two species by observing the anther locule number and then compared the size of the leaf cells in fixed and dried specimens. To identify plant fragments, we examined differences in epidermal cell length and width depending on the position of the cells within the plant. The length and width significantly differed in both fixed and dried leaves between the species. In particular, the epidermal cells of N. oguraensis ( > 160 μm) were about twice as long as those of N. minor regardless of leaf position. We therefore concluded that cell size, especially length, is a valid method for identifying the species in both fresh and dried condition. This method is effective where precise identifications are necessary, such as in floristic surveys and environmental assessments.

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Ludwigia grandiflora (Michx.) Greuter & Burdet is an invasive aquatic plant native to an area ranging from the southeastern United States to South America. In previous reports, L. grandiflora in Lake Biwa has been identified as L. grandiflora subsp. grandiflora, a hexaploid subspecies (2n = 48) or L. grandiflora sensu lato. Species of Ludwigia sect. Jussiaea, are morphologically very similar. Morphological characters, especially floral characters and cytology (chromosome number) have been used to identify species and subspecies. In our study, the morphological characteristics of L. grandiflora in Lake Biwa substantially corresponded to those of L. grandiflora subsp. hexapetala (Hook. & Arn.) G. L. Nesom & Kartesz, a decaploid (2n = 80) subspecies. The chromosome number of L. grandiflora in Lake Biwa was 2n = ca. 80, the same as in L. grandiflora subsp. hexapetala (2n = 80). Importantly, L. grandiflora in Lake Biwa is not L. grandiflora subsp. grandiflora, but rather L. grandiflora subsp. hexapetala. This re-identification has implications for management in Lake Biwa, since the life history of L. grandiflora subsp. hexapetala has been studied in Europe.

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A set of 8 polymorphic EST-SSR markers has been developed to evaluate the genetic diversity and genetic structure of the populations of Tricyrtis sect. Tricyrtis (Liliaceae) in Kyushu, which reproduces sexually and asexually by bulbils. The total number of alleles for each locus ranged from 2 to 11 with an average of 5.5, while the values of observed and expected heterozygosity ranged from 0.043 to 0.875 and 0.043 to 0.849, respectively. The combined probabilities of identity (PI = 6.0E-07 and PI-Sib = 2.7E-03) of these markers suggest that they are useful for not only evaluating genetic diversity but also for estimating clonal diversity within populations. Cross-species amplification was evaluated for three phylogenetically related species, T. macropoda, T. setouchiensis, and T. affinis, to show that all the EST-SSR markers are transferrable among these species.

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