List of Orchid Species Common to Australia and New Zealand. By Edwin D. Hatch, Laingholm, Auckland. [Read before the Auckland Institute, December 12, 1945; received by the Editor, January 10, 1946; issued separately, June, 1946.] The close relationship between the orchid floras of Australia and New Zealand has become more and more evident with the passing of the years. When Hooker published the Flora Novae Zelandiae in 1853, he recognised only three species of orchids occuring both in New Zealand and in Australia. The present account recognises 34 such species, rather less than half the total orchid population of these islands, and an advance of 18 upon Cheeseman's Figure in the 1925 Manual. To the Rev. H. M. R. Rupp, of Sydney, must go the credit for most of the research connected with proving the identity of the species under consideration. All the writer has done, has been to check and confirm the evidence and conclusions presented by Mr. Rupp. Sound reasons for the several changes of name are given in the Proc. Linn. Soc. N.S.W. 70, 1945. (Rupp & Hatch.) In the same paper the anomalous Caladenia bifolia Hook.f. becomes Aporostylis bifolia (Hook.f.) R. & H. Only the current local synonymy has been quoted in the lists that follow. An asterisk following a name indicates that the species has been recorded from New Zealand since the appearance of the 1925 Manual. In these cases a note of the general distribution of the form and its relationships with other New Zealand species, is added. The list has been divided for convenience into two sections— A. Those species in which the New Zealand plant is exactly similar (except for normal epharmony) to the Australian. B. Those species in which the New Zealand plant shows sufficient constant variation from the Australian to warrant varietal rank. It is worth recording here that Thelymitra uniflora Hook. f., which Cheeseman (Manual, 1906, 672) thought might be identical with the Tasmanian Th. cyanea Ldl., is in fact quite distinct. Both belong to the evolutionary group of Th. venosa R. Br., but in Th. uniflora the lateral lobes of the column-wing are spirally involute and entire; whereas in Th. cyanea the lobes are not involute and are irregularly bifid. A. 1. Thelymitra ixioides Sw. Vet. Akad. Handl. Stockh., 21. 1800. 228. t. 3. L. 2. Thelymitra longifolia J. R. & G. Forst. Char. Gen. Plant., 1776. 98. t. 49.