Hydnaceae of New Zealand Part II.—The Genus Odontia By G. H. Cunningham Abstract Odontia is treated as the seventh genus of the family Hydnaceae present in New Zealand. Twenty-five species are recognized. A detailed description of each is given, accompanied by notes on distribution, hosts and comparative features. A diagnostic key to species is appended and all are illustrated with original line drawings of transverse sections and photographs of selected species. Fourteen new species are described, descriptions being accompanied by formal Latin diagnoses. Species previously named and redescribed in detail are O. archeri (Berk.) Wakef., O. arguta (Fr.) Quel., O. barba-jovis (With.) Fr., O. bicolor (A. & Sw.) Bres., O. calcarea (Cke. & Mass.) G. H. Cunn., O. crustosa (Pers.) Quel., O. fimbriata Pers. ex Fr., O. hydnoides (Cke. & Mass.) Hoehn., O. lyndoniae Reid, O. scopinella (Berk.) Cke. and O. subfascicularia (Wakef.) G. H. Cunn. Of these O. arguta, O. barba-jovis, O. bicolor, O. crustosa, O. fimbriata and O. hydnoides are found in Europe, Great Britain and North America, O. arguta extending also to Australia and O. fimbriata to Samoa; O. archeri is recorded from North America, Cuba, Ceylon and Australia; and O. calcarea, O. lyndoniae, O. scopinella and O. subfascicularia were named from Australian collections. Introduction As delimited herein Odontia contains those resupinate species of the family which bear cystidia It is a heterogenous genus containing several groups of related species, inclusion of species depending upon interpretation of what are termed cystidia About 80 species have been described, but the number is uncertain owing to the various interpretations of generic features employed by various authors. The genus contains the largest number of species of those included in the family, found in New Zealand Features of value in specific delimitation are defined below. Hymenophore. Fructifications are effused upon the substratum, usually forming plane areas from the surface of which arise the spines. Most are coloured white or cream, shading through alutaceous to light tints of brown Few are noteworthy because of marked features of surface colouring or configuration. Many extend as an even sheet over the substratum, save for the spines, others are deeply areolately creviced, as in O. calcarea and O. subscopinella. In O. nothofagi the surface is ferruginous with ferruginous spines, and plants possess a roughly orbicular outline. Most species are annual, with one layer of context tissue; in O. stratosa and O. tessellata fructifications consist of several well defined layers indicating several periods of growth. Margins in most species are somewhat similar, thinning out and becoming fibrillose and in colour white or pallid cream In O. tessellata the margin is abrupt and cliff-like, thick and dark in colour. Context. In most species the context is composed of an intermediate layer of intertwined or upright hyphae arising from a basal layer of mainly parallel hyphae either well developed or reduced to a few repent hyphae. Hyphae may be naked, the common condition, or encrusted with calcium crystals; and may enclose masses of crystals so that tissues appear cretaceous, as in O. calcarea, O. crustosa and O. stratosa.