Abstract: A detailed description is given of the new species Archineottia japonica M. Furuse, which is the first member of the genus reported from Japan. Two specimens of this rare plant were collected by the senior author from Yamanashi and Nagano of Honshu respectively. Its habit is very similar to that of Neottia, which is represented in Japan by two species, N. papilligera (=N. nidus-avis var. manshurica) and N. asiatica (=N. acuminata), From them, however, it can be very clearly distinguished by its peculiar column on which nothing is found but a terminal stigma and one erect stamen with rather distinct filament. This is no doubt a very primitive column structure, only found in Archineottia and quite different from that in Neottia (Table l). This Japanese plant is a true Archineottia, from which it shows no difference in column structure. It is akin to A. smithiana of China, and probably also to A. pantlingii of Sikkim, all belonging to the section Furcilla. But it differs much from them by the nearly oblong lip almost equal in length to the petals. Its occurrence in central Honshu of Japan is indeed of phytogeographic interest, indicating the floristic connection of this region with central China and the Himalayas. The genus is now composed of five species. A key to them is provided as follows: l.Lip very similar to the petals, stigma antrorse. (Sect. Archineottia) 2.Sepals oblong or narrowly oblong, as broad as or slightly broader than the petals (Shanxi and Henan of China) ......................................................... A. gaudissartii (Hand.-Mzt.) S. C. Chen 2. Sepals ovate-oblong or ovate, nearly twice as broad as the petals (northwest India) ............... ....................................................................................... A. microglottis (Duthie) S. C. Chen 1.Lip bilobed at the apex, utterly different from the petals, stigma slightly curved forwards. (Sect. Furcilla) 3.Lip nearly oblong, slightly longer than or as long as the petals (Honshu of Japan) .................. ............................................................................................................ A. japonica M. Furuse 3. Lip obovate or nearly cuneate, much longer than the petals. 4.Lip obovate, horizontally spreading, free filament 1/3-1/4 as long as the column (Sichuan and Shaanxi of China) ............................................................ A. smithiana (Schltr.) S. C. Chen 4.Lip nearly cuneate, pointing upwards, free filament about 1/2 as long as the column(Sikkim) ....................................................................................... A. pantlingii (Duthie) S. C. Chen

Key words: Archineottia, A. japonica, Neottia