Arisaema ehimense is morphologically intermediate between A. serratum and A. tosaense. The species is very similar to that of their artificial hybrid, which suggests a hybrid origin between two species. However both species rarely grow in same areas. And furthermore flowering period of A. serratum is earlier than that of A. tosaense. Therefore it has been considered that there is no opportunity of hybridization between the species. In this study we observed the flowering period of the two species at Ohshima in Yamaguchi Pref. where both species grew at same area. There we found that a part of the A. serratum could hybridize a part of A. tosaense. This fact shows that hybridization ought to have occurred between two species. This is an example of hybridization which could generate new species. It also suggests that we need to consider the importance of the habitats where more than two kin species are alive for a new species birth area, and must preserve them.