The variations in some morphological characteristics along with the pigmental ones of Rhododendron kaempferi Planch., R. kiusianum Makino and R. eriocarpum Nakai distributing in southern Kyushu, were investigated.
The populations of R. kaempferi in southern Kyushu showed much wider variations in flower-colour, flower-size and the occurrence of petal-blotch than those in northern Kyushu. Furthermore, in the former populations, anthocyanins of the delphinidin-series co-existed with the commonly occurring cyanidin-series, as compared with the latter whose anthocyanins were confined to the cyanidin-series. Hence, the southern populations of R. kaempferi seemed to have been resulted from the introgressions of other azaleas with anthocyanins of the delphinidin-series to the true forms.
Extremely narrow variations in the morphological and pigmental characteristics were shown in R. kiusianum, suggesting that populations distributing at and around the summit of volcanic mountain, Mt. Karakunidake, represent true species. On the other hand, population of R. eriocarpum at the summit of Mt. Kaimondake showed wider variations in flower-colour and the occurrence of flavonoid pigments than that of Mt. Ontake in Tokara-Archipelago. These variations seen in the former might be the result of the introgression of R. kaempferi occurring near the habitat of R. eriocarpum at the summit of Mt. Kaimondake.
In any case, the populations of R. kaempferi and R. eriocarpum in southern Kyushu exhibited wider variations and contained many peculiar individuals with respect to their floral characteristics. Therefore, we can easily adopt the more promising germplasms as the materials of future breeding among their natural variations.