Abstract
We studied the plants which had been identified as Typha laxmannii Lepech. (Typhaceae) in Hyogo Pref., Japan (hereafter "Typha laxmannii."). We compared five morphometric characters of the shoots, the presence or absence of bracteole in female flowers and the pollen size among the population of "Typha laxmannii", 16 populations of T. angustifolia L. from Hyogo Pref. and one population of T. laxmannii from Akita Pref.. "Typha laxmannii" from Hyogo was not distinguished from T. angustifolia based on the morphometrical characters. On the other hand, T. laxmannii from Akita Pref. was distinguishable by the width and length of the leaves from rest of the populations. The bracteole was present both in "Typha laxmannii" from Hyogo and T. angustifolia, but absent in T. laxmannii from Akita. Pollen size was significantly larger in T. laxmannii from Akita, but it was not different between "T. laxmannii" from Hyogo and T angustifolia. Based on these facts, we conclude that "T. laxmannii" from Hyogo is a variation of T. angustifolia and that T. laxmannii from Akita has been identified correctly. This research confirmed the occurrence of T. laxmannii in Japan. Although T. laxmannii in Japan is treated as alien species in recent literature, we suggest the possibility that it is an endangered species native to Japan.
