Abstract

An intensive survey of the habitat and habit of Erythrorchis altissima (Bl.) Bl., a chlorophyll-free twining orchid from Kutinoerabujima and Tokunoshima islands, at the southernmost part of the Japanese Archipelago, and at the northernmost end of the range of the orchid, showed that (1) the species inhabits forests dominated by Castanopsis sieboldii, (2) the terrestrial stems climb almost exclusively on trunks of C. sieboldii, especially on trunks of dead trees, (3) the species frequently occurrs on "hodagi" made of C. sieboldii, the bed logs (1-1.5m long) for the cultivation of "Shiitake" mushrooms, Lentinus edodes (this suggests that "hodagi" provides a source of the symbiotic mycorrhizal fungi for the orchid), (4) the average length of terrestrial stems in plants bearing flowers was 3.5m, ca. 2m longer than sterile stems (this suggests that the terrestrial stems require a considerable time to grow before flowering) and (5) the species flowers from May to June and fruits mature in November.