The genus Lespedeza Michaux was described by Richard in 1803 (Nakai, 1925; Ricker, 1934; Hochreutiner, 1934) based on a North American species, L. sessiliflora Michx. (now regarded as a synonym of L. virginaica (L.) Britton). A detailed account of the taxonomic history of the genus Lespedeza covering the period up to 1873 is given in a monograph on this genus by Maximowicz (1873).

The generic delimitation of Lespedeza was controversial. Maximowicz (1873) regarded Campylotropis, Lespedeza, and Microlespedeza as subgenera of the genus Lespedeza. Schindler (1912) raised the subgenus Microlespedeza of Maximowicz to a new genus, Kummerowia. Based on its inflorescence and other characters Schindler (1913) recognized the three subgenera of Maximowicz as distinct genera and also recognized two sections in the genus Lespedeza, sect. Macrolespedeza and Eulespedeza (= Lespedeza), as did Maximowicz (1873).

Although Nakai (1927) regarded Campylotropis as congeneric with Lespedeza, he recognized no subgenera and only three sections in Lespedeza: Campylotropis, Macrolespedeza, and Eulespedeza. Kummerowia was regarded as a distinct genus by him. Nakai (1939) established the section Heterolespedeza based on Momiyama's observation of bud phyllotaxy in L. Buergeri (Momiyama, 1933), and L. Maximowiazii is also included in this section.

Ohashi (1971) recognized Lespedeza and Kummerowia as distinct genera and Campylotropis as congeneric with Lespedeza in his study of the tribe Coronilleae. But later, he regarded Kummerowia as congeneric with Lespedeza, while Campylotropis as a distinct genus (Ohashi, 1982b). Ohashi (1982a) also recognized Macrolespedeza as a sub-genus in the genus Lespedeza. This subgenus, according to him, consists of two sections, Macrolespedeza and Heterolespedeza. We studied the branching pattern of the vegetative shoots and the inflorescences of Kummerowia and gave evidence for the distinguishing between Lespedeza and Kummerowia (Akiyama & Ohba, 1985).

In the section Macrolespedeza Maximowicz recognized five species three of them reported from Japan. Schindler (1913) examined almost all the type and authentic specimens, and then revised the taxonomy. He recognized eight species in sect. Macrolespedeza, four of them from Japan.

Nakai studied Japanese and Korean species of Lespedeza, chiefly herbarium specimens, and used various combinations of vegetative characters to distinguish the species but paid little attention to floral features. In 1927 he published. "Lespedeza of Japan and Korea." This is regarded as a standard work on species growing in the two countries. He recognized 18 species in sect. Macrolespedeza of which 14 are from Japan, including seven new species. He also regarded ten species as endemic.

Hatusima (1967) studied the species and the infraspecific taxa under sect. Macrolespedeza and Heterolespedeza from Japan, Korea, and Taiwan. He partially evaluated the importance of the characters used by Nakai (1927) and others including Ohwi (1953, 1965a, b) and Kitamura & Murata (1961). His evaluation, however, depended on personal impressions, and are unsatisfactory. He did not attempt to find significant characters within flowers and did not mention the floral features except for the calyx. No revision has been published after that, although some of the Japanese species belonging to sect. Macrolespedeza were discussed by Murata (1978) and Ohashi (1981, 1986).

Interspecific hybridization is known in both sections of Lespedeza, sect. Lespedeza (Clewell, 1964, 1966) and sect. Macrolespedeza (Lee, 1965). Clewell revealed the intermediate appearance of morphological characters as well as cytological evidence and pollen stainability for detecting interspecific hybridization. However, Lee did not mention any concept or criteria to distinguish the hybrids from the species recognized by him. We studied the interspecific hybridization of sect. Macrolespedeza in Japan (Akiyama & Ohba, 1982, 1983a, c), and judged the occurrence of hybrids from the intermediate appearance of morphological characters and some reduction of pollen stainability (Akiyama & Ohba, 1982). We also noticed the occurrence of introgressive hybridization which shows a morphological continuity and irregularity in the reduction of pollen stainability (Akiyama & Ohba, 1983a).