Thelephoraceae of New Zealand Part III: The Genus Corticium By G. H. Cunningham, Plant Diseases Division, Auckland [Read before the Auckland and Institute and Museum, September 14, 1953, received by the Editor, February 9. 1954] Abstract Corticium is treated as second of seven genera placed in the tube Corticeae of the subfamily Thelephoioideae. Forty-two species are recognized, of which 21 are regarded as new. A diagnostic key to species is given together with a full technical description of each accompanied by notes on distribution hosts and comparative features. Thirty-eight are illustrated with line drawings of sections. two with drawings of spores, and three with photographs. Twenty-one new species belonging to the genus in New Zealand are described and figured. Excluded species, based on identifications of specimens by overseas workers, are C. albidum Mass., C. auberianum Mont, C. calceum (Pers) Fr, C. ceraceum Berk. & Rav… C. cretaceum Pers., C. laeve Pers, C. luteo-aurantiacum Wakef, C. molle Fr, C. nudum Fr, C. ochaceum Fr, C. polygonium (Pers) F1. C. sebaceum (Pers.) Mass. C. serum (Pers.) Fr, C. sparsum Berk. & B1, C. spumeum Berk & Rav, C. sulfureum Fr. C. terreum Berk. C. violaceo-lividum Fr., C. de Berk and C. viscosum Fr. Introduction Corticium is the second genus placed in a previous paper (Cunningham, 1953) under the tribe Corticeae of the subfamily Thelephoroideae It contains species with an even hymenium consisting of a palisade of basidia and paraphyses, developing from a context composed of woven or upright hyphae arising in turn from a layer of parallel hyphae attached to the substratum Most species are wood-inhabiting, a few grow upon debris on the ground, and a half-dozen are parasites of living plants. The genus contains many species, possibly in excess of 300, but as most grade into one another, and well-marked specific features are few and difficult to define precisely, it is not possible to ascertain their number. Different workers have placed emphasis on diagnostic features which are often variable and of trivial value; so that what are regarded as species by some, are treated by others as varieties, forms, or synonyms. Even when authentic material is available for study, identification of collections is often difficult because of variations which may occur in features upon which species were erected. The value of differential characters employed by various workers is discussed below. In 1951, through the courtesy of the Director of the Royal Botanic Gardens, Kew, I was enabled to examine collections of all species of the family in Kew herbarium These included authentic or type specimens described from Europe