Other specimens examined: Cook Islands: Totokoitu Valley, on Metrosideros sp., 19 Oct. 1975, J. Dugdale (PDD 34722); Te Rua Manga, on Metrosideros collina, 15 Mar. 1975, R.A. Fullerton (PDD 35433).

Colonies are black, scattered, up to 4.5 µm diam., larger by confluence, densely velutinous with a thin hyphal fringe. Leaf tissues (of dried leaves) around the colonies are tinged with pink, and corresponding discolourations are also found on the upper surface. Superficial hyphae are cylindrical, straight or slightly flexuous, branched, radiating, brown to dark brown, paler toward their ends, 5.5-7.2 µm wide, septate at (32-)45-70 µm intervals with the appressed wall thinner than the thickened exposed wall. Stomatopodia are scanty and scattered, cylindrical to ellipsoidal, entire or once lobed and up to 34 x 7.3 µm. Ingress cells are subhyaline to pale brown, ellipsoidal to subglobose, 12.5-20 x 10-15.3 µm. They frequently develop singly from intercalary cells of superficial hyphae or on a small lobe of such cells. Collodion preparations show abundant egress cells and it appears that most if not all superficial hyphae are derived from these. Egress cells are subglobose, 12.5-17 µm diam.; they generally arise in pairs from paired cells within a suprastomatal chamber, and may be scattered but often occur in groups of ten or more. Egress cells can produce up to five hyphae which extend over the leaf surface. Phialophores usually develop early on hyphae close to their origin from egress cells: accordingly, maturing colonies frequently show separate concentrations of phialophores. Confluence of mini-colonies produced from groups of egress cells contribute to the dense, uniformly velutinous part of mature colonies. Phialophores are up to 260 µm long, (2-) 3-4 (-5)-dichotomously branched and arborescent, but generally the stalk before the first dichotomy is short, 5.4-8 µm wide, tapering gently to 3.8-4.7 µm, wide toward the ends of the branches, dark brown toward the base, distally brown to pale brown and bearing a single phialide at the ends of the branches. Phialides are subulate to very narrowly obclavate, 28-47 µm long, pale brown to brown at the base and pale brown to subhyaline and 2-2.7 µm wide below a hyaline, funnel-shaped collarette. Phialoconidia minute. Perithecia are central, few to each colony, black, subglobose, dorsiventrally flattened, bearing on their lower part irregularly radiating, sparingly branched, cylindrical to nodulose pale brown to brown hyphae. The upper part bears numerous straight or slightly curved setae, up to 200 µm long but usually shorter, 6.3-8.1 µm wide and dark brown below, tapering to 1.8-2.7 µm at a brown rounded apex. Paraphyses are abundant, persistent, more or less cylindrical, septate, often paired and arising from short obovoid cells: they are 5-6 µm wide below tapering to 3.5-4 µm wide at the rounded apex. Asci are narrowly obovoid to clavate, thick-walled throughout when young but more or less undifferentiated at the apex and (6-)8-spored. Discharged asci are 153-180 µm long and have a broad apical opening. Ascospores are ellipsoidal to subcylindrical, sometimes slightly more tapered toward the base, brown to dark brown with a wide, conspicuous dark brown to black band of wall over the septa, usually straight, occasionally very slightly curved, slightly to scarcely constricted at the septa. The central cells are more or less doliiform to subcylindrical and wider than long, and the end cells more or less hemi-ellipsoidal to hemispherical and the lower end cell often tapered and occasionally subconical. Polar caps are dark brown to almost black, and convex to subconical. A conspicuous subhyaline to very pale brown band is found immediately below the polar caps and on each side of the dark septal bands. Ascospores measure 43.2-65 x 15.3-20 (-22.5) µm.

Distribution: Cook Islands (Rarotonga).

Host species: Metrosideros collina (J.R. Forst.) A. Gray, M. sp.

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Notes: The three collections cited above were reported as M. sydowiana F. Stev. by Dingley, Fullerton & McKenzie (1981). Meliolina cookii differs from M. sydowiana in having smaller colonies, shorter phialophores, and smaller ascospores which are more obtusely rounded at their ends and the eight pale bands are more conspicuous. Colonies of M. cookii are larger than those of M. degeneri and have a thin hyphal fringe, phialophores are more profusely branched, ascospores are wider, and egress cells are abundant and conspicuous.

Typification: Cook Islands: Avatiu Valley, on Metrosideros collina, 4 Oct. 1975, J.M. Dingley (PDD 34721, holotypus).