Peridiscus lucidus Benth. was first found by Spruce on the Rios Uaupes and Pacimoni and was recently collected near Manaus ( on the Rio Tarumi) by the late Dr. A. Ducke. Originally described by Bentham (1862) in the 'Genera Plantarum', it was figured with a fresh description by D. Oliver (1896) in Hooker's 'Icones Plantarum'. These authors both placed it, with some doubt, in the Bixaceae and it was maintained in that family by Eichler (1871) in Martius's 'Flora Brasiliensis', and at the end of the Flacourtiaceae, with doubt, by Dr. O. Warburg (1893) and E. Gilg (1925) in the first and second editions of the 'Pflanzenfamilien'. Recently, however, the plant has been studied afresh from Ducke's much better material, by Dr. J. G. Kuhlmann (I950). This author, who was apparently ignorant of Oliver's figure and description, after pointing out errors in the descriptions of Bentham, Eichler, Warburg and Gilg, rejected Peridiscus, not only from the Flacourtiaceae, but also from the Olacaceae and, finally, the Capparidaceae, in which latter family it had been placed by H. Hallier (I908). He proceeded to treat it as constituting a new family Peridiscaceae, the salient characters being the presence of stipules, apetaly, imbricate sepals, numerous stamens with monothecous anthers, a conspicuous disk surrounding the unilocular ovary, pendulous ovules from its apex, 3-4 free styles, a large, solitary seed with abundant horny endosperm, and a minute, straight embryo placed laterally in a shallow cavity near its apex. The characters of the endosperm and the embryo, he noted, are found in the Santalales. The family Peridiscaceae is accepted by Dr. J. Hutchinson (I959) in the new edition of his 'Families of Flowering Plants', and is placed in the Tiliales, 'for want of a better place', but he seems not to have read Kuhlmann's emended description and comments, for he repeats the errors of his predecessors, describing the sepals as valvate, the anthers (also figured) as 2-locular and the seed as without endosperm. Some of these characters could have been verified by examination of Ducke's specimens of Peridiscus lucidus at Kew. Again, it must be stated that the Peridiscaceae appears in Hutchinson's great 'Key to the Families' in a section with exstipulate leaves on p. 91, under Group 12, although he rightly mentions the stipules in his description of the family. The Potaro Valley material lacks fruits and seeds, but shows nearly all