The pollen grains of Japanese Lespedeza were studied by Ikuse (1956) in L. bicolor, L. cyrtobotrya, and L. Buergeri, and she reported no difference in pollen type or pattern and only slight differences in size. The pollen grains of these species are tricol porate and classified as type 6B^b by her, while the form of the exine is subreticulate. The size of L. bicolor is 19.5-21 × 19.5 µm, somewhat smaller than those of L. cyrtobotrya and L. Buergeri which are 21-22 × 19.5-21 µm.

Ohashi (1971) examined the pollen grains of the tribe Coronilleae, including L. bicolor of sect. Macrolespedeza, some species of sect. Lespedeza, and some species of Campy lotropis. In Lespedeza and Campylotropis the pollen grains are rather uniform and tricolporate. Ferguson & Skvaria (1981) surveyed the pollen grains of the subfamily Papilionoideae morphologically and pointed out that in the tribe Desmodieae (including Lespedeza and allied genera in the adapted system) the pollen is diverse in shape, of the tectum type in wall stratification. The tricolporate apertures generally lack an aperture membrane, and a thick endexine without the very thin foot layer which characterizes the pollen of the tribe. They did not examine pollen grains of Lespedeza, however.

In the present study we examined the pollen grains of L. bicolor, L, Buergeri, L. cyrtobotrya, L. formosa subsp. velutina, L. formosa subsp. velutina var. satsumensis, L. homoloba, L. Maximowiczii, L. melanantha, L. patens, and L. Davidii; four species of sect. Lespedeza: L. pilosa, L. cuneata, L. tomentosa, and L. virgata\ and two species of the genus Kummerowia for comparison. Pollen grains were taken from herbarium specimens, coated with platinum, and examined with a scanning electron microscope (Hitachi S-700). The pollen grains of Lespedessa are tricolporate and subreticulate (Plates 5 & 6). Pollen morphology of Lespedeza shows no specific diversity. The size of the pollen grains of Lespedeza is also nearly the same among species (Plates 5 & 6A-E). The shape of the pollen grains of Kummerowia is also similar to that of Lespedeza, but the exine sculpture is somewhat different. The reticulation is not so clear as in Lespedeza (Plate 6F).