Abstract
Carex planata has been treated as comprising three varieties: var. planata, var. angustealata, and var. remotiuscula. To evaluate this treatment, characteristics of the inflorescences, spikes, utricles, and achenes of both herbarium specimens and growing plants in the field were examined. Principal component analysis (PCA) revealed two distinct groups within C. planata, one of which was identical to var. angustealata and the other to var. planata; var. remotiuscula could not be distinguished from var. planata. Variety remotiuscula was confirmed to be a synonym of var. planata. Variety angustealata of western Japan grows in flood plains along rivers. The results from PCA and information from distribution and habitat led to the conclusion that var. angustealata should be treated as a distinct species: C. angustealata, characterized by ascendant utricles and a greater number of spikes (≥ 9) on well-grown plants. Smaller achenes in proportion to the utricles also distinguish C. angustealata from C. planata. Detailed descriptions of both C. angustealata and C. planata based on the numerical survey are presented. Lectotypes of var. angustealata Akiyama and var. remotiuscula Akiyama are designated.
