Sooty blotch on Metrosideros spp. is common in New Zealand in scattered localities where rainfalls are heavy. It is an endemic fungus described on endemic species of Metrosideros.

Type: Sooty Moulds and Similar Fungi; Description: Subiculum densely velutinous, up to 15 mm in diameter, black; on the lower surfaces of leaves. Mycelium reticulate, composed of brown to pale brown, septate, cylindrical, straight or slightly curved, 6–9 μm wide hyphae which become paler towards their distal ends, with numerous, erect, mostly simple mycelial setae, up to 450 μm long. Stomatopodia abundant, variously shaped, entire or once-lobed, up to 30 μm long. Ascomata perithecial, scattered, black, depressed globose, up to 0.5 mm in diameter, ostiolate, the upper half bearing numerous erect, simple, black setae, up to 250 μm long. Asci clavate to ovate, 150 × 50 cm. Ascospores cylindrical, 3-septate, 45–65 × 18–25 μm, dark brown. Conidia cuneiform, 0-septate, 4–5.5 × 2.2–2.7 μm, hyaline.

Distribution: Kermadec Islands, Northland, Auckland, Coromandel, Bay of Plenty.; 1st Record: Hansford (1954).

Significance: None.; Host(s): Metrosideros excelsa, M. kermadecensis, M. robusta.

The colonies are hypophyllous, up to 10 mm. or more in diam. or widely confluent, black, densely velvety. External mycelium of dark brown hyphae creeping over the leaf and forming stomopodia over the stomata, from which the internal mycelium enters the leaf and penetrates most of the mesophyll as intercellular, hyaline, septate hyphae which do not form haustoria in the host cells. Mycelial setae numerous, erect, mostly simple and obtuse to somewhat attenuate at the apex, up to 440 x 8-10 µ, or some forked irregularly with branches up to 120 µ long. Perithecia scattered amongst the mycelial setae, black, depressed-globose, the upper half bearing numerous erect-spreading simple black obtuse setae, up to 250 µ long; perithecia up to 500 µ diam. and 250 µ high, opening by a rounded pore at the vertex; the wall consists of an outer layer of rounded-polygonal cells which are slightly prominent, hence the surface appears slightly verrucose, passing internally into a hyaline mass of soft parenchyma, at first filling the whole interior. Within this soft tissue the fairly numerous asci develop from the base, replacing the original ground tissue, the remains of which form the more or less evanescent septate "paraphyses". Asci widely clavate to ovate, rounded at the apex and when young thickened there to 10 µ, nodose-stipitate below, 8-spored, about 150 x 50 µ. Spores cylindric to slightly ellipsoid, obtuse at the ends, dark brown, 3-septate, slightly constricted,. 45-55 x 18-21 µ, the cells approximately equal in length and the middle ones not noticeably swollen; end cells with the subterminal and sub-basal narrow hyaline bands usual in this genus.

Plagulae hypophyllae, usque ad 10 mm. diam., vel late confluentes, atrae, dense velutinae. Mycelium ex hyphis atrobrunneis, irregulariter ramosis, exhyphopodiatis, repentibus compositum, supra stomata folii stomopodia efformans et mesophyllum penetrans. Setae myceliales numerosae, erectae, simplices vel irregulariter furcatae, ramulis usque ad 120 µ longis, apice obtusae vel leniter attenuatae, usque ad 440 µ alt. et 8-11 µ cr. Perithecia dispersa, atra, depresso-globosa, usque ad 500 µ diam. et 250 µ alt., sursum setulosa; setae numerosae, simplices, atrae, obtusae, usque ad 250 µ longae; paries perithecii extus verrucosus, parenchymaticus, cellulis rotundato-polygonalibus, leniter prominentibus, atrobrunneis, intus in massam hyalinam mollem transeuntibus. Asci sat numerosi, basales, ereeci, ovati vel late clavati, apice rotundati, nodoso-stipitati, circa 150 x 50 µ, 8-spori. Paraphyses hyalinae, septatae, 3-5 µ cr., evanescentes. Sporae 2-3-seriatae, cylindraceo-ellipsoideae, utrinque obtusae, 3-septatae, leves, 45-55 x 18-21 µ.

Hab. in foliis Metrosiderodis excelsae, Rangitoto Is., Auckland, New Zealand, Dingley, July 1950, in Herb. Division of Plant Diseases, Auckland, N.Z.

Other specimens examined: New Zealand: Piha, on Metrosideros excelsa. 31 July 1967, JD. Reid (PDD 26005); Piha, on M. excelsa. 18 Sept. 1970, J.M. Dingley & B.S. Parris (PDD 28580); Little Barrier Is, Thumb Track, on M. excelsa, 30 Aug. 1958. J.M. Dingley (DAOM 142247, PDD 18482); Poor Knights Is, Tawhiti Rahi, on M. excelsa, 6 Dec. 1969, B.S. Parris (PDD 28427); Russell, on M. excelsa, 16 Sept. 1967, J.M. Dingley (PDD 26067); North Cape, Whiriwhiri Stream, on M. excelsa, 29 Mar. 1970, B.S. Parris (PDD 28428); Ngaiotonga Ra., nr Russell on Metrosideros robusta, 17 Sept. 1967, J.M. Dingley (PDD 26080); Little Barrier Is (1500'), on Metrosideros umbellata, 1 Sept. 1958, J.M. Dingley (PDD 18495, IMI 86116).

Colonies are black, up to 15 mm diam., larger by confluence, centrally densely velutinous, gradually less so toward the margin, with a hyphal fringe partially hidden in the tomentum. Superficial hyphae are cylindrical, straight or slightly sinuous to irregularly bent, more or less radiate at the margin, centrally much branched and appearing reticulate, brown to pale brown, paler at their ends, 6.3-9 µm wide and septate at 30-75 µm intervals with the wall adjacent to the leaf surface somewhat thinner. Hyphae may bear numerous short lateral branches; some are upturned and destined to form phialophores and others are appressed stomatopodia. Stomatopodia are abundant, variously shaped, ellipsoidal to subcylindrical to subglobose to ovoid or obovoid, straight or curved, entire or once lobed, up to 30 µm long and 6.5-12 µm wide Entry of the fungus into the leaf via the stomata is not as uniform as in other species of Meliolina: this may be due, in part at least, to the large, domed, suprastomatal chambers, raised above the general level of the epidermis, and which have inside dimensions of up to 23 µm long, 16 µm wide and 14-20 µm high. When a stomatopodium overlies a stomatal opening a hypha arises from its appressed surface and swells, partly or entirely within the suprastomatal chamber, into a globose, dark brown, thick-walled cell 10.5-11.5 µm diam.: this cell then produces a brown to pale brown, thinwalled, ellipsoidal to sublimoniiform ingress cell up to 27 µm long and 12.5 µm wide which is appressed to the guard cells (e.g. Fig. 72A). The stomatal pore is penetrated by a wide, 12.5-16 µm, very narrowly ellipsoidal to flattened hypha 1.5-2 µm thick derived from the ingress cell. Within the substomatal chamber the penetrating hypha expands and produces several compact, brown cells from which hyaline hyphae extend intercellularly in the leaf tissues. Commonly an ingress cell may be produced directly from a stomatopodium without the intervention of a globose cell. Globose cells and/or ingress cells can also develop directly from intercalary cells of superficial hyphae or on a small lobe of such cells. Frequently two stomatopodia, which can arise as paired outgrowths of the same cell of a hypha, of neighbouring cells of the same hypha, or of cells of different hyphae, may overlie the same stoma; such stomatopodia may be parallel or otherwise contiguous. Globose cells and/or ingress cells develop from these and fill the suprastomatal chamber, and they may show the same kind of variation as found when only a single stomatopodium is involved, but two narrowed hyphae arising from the two egress cells may penetrate between the guard cells. Uncommonly, three stomatopodia may overlie a stoma and each can contribute cells to a crowded and dilated suprastomatal chamber. Egress cells are scanty and composed of single very dark brown cells which give rise to 2 or 3 superficial radiating hyphae. The egress cells arise from solitary, large ellipsoidal cells occupying suprastomatal chambers and derived from a hypha within the substomatal chamber. Phialophores up to 250 (-350) µm long, setiform, centrally densely crowded, marginally scattered, simple or 1-2(-3)-dichotomously branched, erect, arising from superficial hyphae. Toward the base they are 6.3-9 µm wide and very dark brown, tapering gradually to 5.3-6.2 µm toward their brown ends which bear a single phialide. Phialides are 30-41 µm long, brown to dark brown below, distally pale brown to subhyaline, more or less cylindrical, below then tapering to 2.3-2.7 µm wide below a funnel-shaped collarette. Phialoconidia cuneiform, hyaline, 4.1-5.5 x 2.2-2.7 µm. The ends of simple phialophore-like erect setiform structures may lack a terminal phialide and taper to a bluntly rounded apex. One or more branches of divided phialophores may also lack a terminal phialide. Perithecia are black, subglobose, dorsiventrally flattened with an ostiole at maturity, up to 400 µm wide, bearing on their lower part, irregularly radiating, simple, straight or sinuous, cylindrical brown hyphae 5.3-6.3 µm wide. On their upper part perithecia bear simple, thick-walled, septate setae which are very dark brown to almost black toward the 6-9 µm wide base, tapering gradually to a bluntly rounded apex 1.8-4.5 µm wide. Paraphyses abundant, persistent, more or less cylindrical, septate, occasionally branched at the base: they are ca 5.5 µm wide toward the base, tapering to 3.5-4.5 µm wide toward the rounded apex. Asci obovoid and thick-walled throughout when young, more or less undifferentiated at the apex and (6-)8-spored. Discharged asci are narrowly ellipsoidal, 165-195 µm long with a broad opening 9-12.5 µm wide. Ascospores more or less broadly ellipsoidal to subcylindrical, brown to dark brown, straight, constricted at the septa, sometimes with a narrow dark band of wall at the septa. The central cells are wider than long, doliiform, and the end cells hemispherical to broadly hemi-ellipsoidal, the lower one being slightly narrower and rarely slightly tapered. Polar caps are dark brown, and convex. A conspicuous, narrow, pale brown to subhyaline band is found immediately below the polar caps and near the septum of each end cell: very inconspicuous pale bands have been seen in some central cells. Ascospores measure 43.5-65(-70) x 19-24(-25) µm.

Distribution: New Zealand (Auckland Prov.).

Host species: Metrosideros excelsa Sol. ex Gaertn., M. robusta A. Cunn., M. umbellata Cav.

Notes: Dingley (1969) remarked that Meholina novae-zealandiae, a `sooty blotch on Metrosideros spp. [M. excelsa (Hansford, 1954b) and M. umbellata (Brien & Dingley, 1959)] is common in New Zealand in scattered localities where rainfalls are heavy. It is an endemic fungus described on endemic species of Metrosideros.'

Typification: New Zealand: Rangitoto Is., on Metrosideros excelsa, 18 July 1950, J.M. Dingley (DAOM 142248, isotype, PDD 12088, holotype).