Type: Sooty Moulds and Similar Fungi; Description: Subiculum circular, velutinous, up to 1 mm in diameter but often confluent, dark brown to black; on leaves. Mycelium composed of dark brown, cylindrical, straight or curved, 9–11 μm wide hyphae which taper and become paler towards their distal ends. Stomatopodia absent. Ascomata perithecial, one or occasionally two to a colony, black, subglobose, up to 0.4 mm in diameter, ostiolate, bearing on the upper part simple, straight or curved, dark brown, thick-walled setae up to 150 μm long. Asci obovoid, 150 μm long. Ascospores subcylindrical, straight, 3-septate, 45–60 × 12–16 μm, dark brown. Conidia cuneiform, 0-septate, 3–5 × 2–2.5 μm, hyaline.

Distribution: Auckland, Taupo, Dunedin.; 1st Record: Dingley (1969: as Meliolina mollis).

Significance: None.; Host(s): Kunzea ericoides, Leptospermum scoparium.

Other specimens examined: New Zealand: Centennial Track, upper Piha Valley, Waitakere Range, on `L. scoparium', 2 May 1963, J.M. Dingley (DAOM 159759); Kawau Island, on `L. ericoides', Oct. 1949, D.W. Mackenzie (PDD 16068, DAOM 75779). Two other collections are also herein assigned to M. leptospermi, but the portions seen lack perithecia: these are Near Brown's Bay, on `L. scoparium', Oct. 1950, J.M. Dingley (PDD 16076, DAOM 142246, IMI 86113); Cascade Kauri Park, on `L. ericoides', 11 Oct. 1964, J.M. Dingley (PDD 23855).

Colonies are mostly hypophyllous, occasionally also with a smaller epiphyllous colony directly above; they are dark brown to black, circular, up to 1 mm diam. but often coalescent to form compound colonies up to 3.5 µm long, velutinous, with a very narrow fringe of appressed hyphae. Superficial hyphae are apparently derived entirely from egress cells. They are much branched, crowded, cylindrical, here and there nodulose, straight or flexuous or irregularly bent, 9-11 µm wide and dark brown at their origin from egress cells, then tapering to 5.5-7.5 µm wide and brown to pale brown toward their ends. Cells of hyphae are 14.5-18 µm long at their origin, increasing distally up to 54 µm. Stomatopodia are apparently absent. Egress cells are abundant, occurring singly or occasionally in adjacent pairs, and they bear an elliptical scar of the hypha which emerged from within the leaf via the stoma: they are subglobose to ellipsoidal, 12.5-20 x 14.5-18 µm, dark brown, and they give rise to 3 or 4 superficial hyphae, some of which radiate irregularly on the leaf surface whereas others turn away from the colony and develop into phialophores. Sections through colony and leaf show that the cell within the suprastomatal chamber is derived from a very dark brown elliptical hypha as narrow as 2 µm and as broad as 6.5 µm which penetrates between the guard cells. This hypha is expanded to 12.5-14.5 µm within the substomatal chamber and is one of several similar, brown to subhyaline, subglobose to ellipsoidal cells connected to hyaline ca. 3.5 µm wide intercellular hyphae in the mesophyll and palisade tissues of the leaf. Phialophores arise from superficial hyphae and also directly from egress cells: they are up to 200 µm long but often shorter, erect at the centre but marginally somewhat repent to upwardly curved, simple or 1-3(-4) dichotomously branched and mostly flexuous. Toward the base they are brown to dark brown, 6.5-9 µm wide, tapering gradually to 4.7-7.2 µm toward the brown ends of the branches which bear a single or paired phialides. Phialides are 34-61 µm long, 4.7-7.2 µm wide and brown to pale brown below, straight or slightly curved, subulate to subcylindrical in the lower part and then tapering to 1.8-2.3 µm and pale brown to subhyaline below a funnel-shaped collarette. Phialoconidia are cuneiform, hyaline and 3-5 x 1.8-2.5 µm and sometimes form short chains. Perithecia are black, nearly always one or occasionally two to a colony, subglobose, dorsiventrally flattened, up to ca. 450 µm wide, ostiolate at maturity, bearing on their lower part dense, irregularly radiating, simple and branched, sinuous or irregularly bent, cylindrical brown hyphae 4.5-5 µm wide, occasionally bearing slender, simple or once dichotomously branched phialophores. On their upper part perithecia bear simple, straight or curved, thickwalled setae up to 150 (-200) µm long which are dark brown below and slightly paler above: they are 6.3-8.5 µm wide toward the base, tapering gradually to 3-4.8 µm wide at the bluntly rounded apex. The latter structures occasionally terminate^- in a single phialide. Paraphyses are abundant, persistent, simple or infrequently branched, septate, surrounded by a mucilaginous layer, arising singly or in pairs from subglobose to ellipsoidal cells: they are 6.3-7.2 µm wide toward the base, tapering gradually to 2.7-4.5 µm wide toward a rounded apex. Asci are obovoid, thick-walled throughout when young, more or less undifferentiated at the apex and 8-spored but sometimes only 6 or 7 mature fully and one or two initials may become pigmented whilst still small. Discharged asci are up to 155 µm long. Ascospores are subcylindrical, often very slightly narrowed toward the base, mostly straight, sometimes curved, dark brown, scarcely constricted at the septa and surrounded by a gelatinous sheath. The central cells are subquadrate to oblong to doliiform, and the end cells are mostly hemi-ellipsoidal, seldom hemispherical and generally longer than the central cells, with the basal cell the longest. Polar caps are brown to dark brown and convex. A conspicuous, narrow, subhyaline band is found immediately below the polar caps and near the septum of each end cell. Slightly thinned zones of wall can sometimes be seen next to the septa of each central cell but not all are associated with a paler band. Ascospores measure (39-)45-60 (-70) x 12.5-15.5 (-18) µm.

Distribution: New Zealand (Auckland Prov.).

Host species: Leptospermum scoparium J.R. & G. Forst., and Kunzea ericoides (A. Rich.) J. Thompson.

Coloniae plerumque hypophyllae, atrobunneae vel atrae, ad 1 mm diam., dense velutinae, ad marginem hyphis brevissimis appressis fimbriatae: aliquando coloniae coalescentia ad 3.5 µm lat. Mycelium superficiale ex hyphis densis, ramosissimis, atrobrunneis vel fere atris, cylindricis, hic illic nodulosis, rectis vel flexuosis vel irregulariter geniculatis, plerumque 5.5-7.5 4 µm cr. compositum: cellulae ad 54 µm long. Nec stomatopodia nec cellulae ingredientes visa. Cellulae egredientes abundantes, subglobosae vel ellipsoideae, 12.5-20 x 14.5-18 µm, singulatim vel binatim oriundae, 3 vel 4 hyphas repentes gerentes. Phialophora in hyphis superficialibus et aliquando in cellulis egredientibus gerentia, ad 200 µm alt., setiformia, 1-3 (-4)-dichotome ramosa et plerumque flexuosa, basim versus brunnea vel atrobrunnea, 6.5-9 µm cr., apicem versus brunnea, 4.7-7.2 µm cr.; rami in phialide unica ve12 divergentibus terminantes. Phialides 34-61 µm long. subulatae vel subcylindricae, rectae vel curvatae, basim versus brunneae vel pallide brunneae, apicem versus pallide brunneae vel subhyalinae, 1.8-2.3 µm cr. et collario praeditae. Phialoconidia cuneiformia, hyalina, 3-5 x 1.8-2.5 µm, aliquando in catenis brevibus orientes. Perithecia solitaria, aliquando binatim in fere omni colonia, atra, subglobosa, ad 450 µm diam., ostiolata, setis supra lateraliterque, crasso-tunicata, simplicibus, rectis vel curvatis, atrobrunneis, ad 150 (-200) µm long. basim versus 6.3-8.5 µm cr., apicem versus 3-4.8 µm cr. et pallidioribus, praedita. Paraphyses abundantes, persistentes, septatae, simplices vel semel ramosae, basim versus 6.3-7.2 µm cr., apicem versus angustiores, 2.7- 4.5 µm cr., singulariter vel binatim in cellulis basalibus subglobosis vel ellipsoideis orientes. Asci obovoidei, juniores crasso-tunicati, vulgo 8-spori: asci emissi ad 155 µm long. Ascosporae subcylindricae, basim versus saepe parum angustatae, plerumque rectae aliquando leniter curvatae, cum taenia atra super septa, magnitudine variantes, (39-) 45-60 (-70) x 12.5-15.5 (-18) µm, ad septa vix constrictae. Cellulae centrales oblongae vel doliiformes. Cellulae terminales plerumque hemi-ellipsoideae, utraeque cum zonis 2 subhyalinis angustis tenui-tunicatis, una sub disco terminali et altera prope septum praeditae. Aliquando cellulae centrales cum zonis 2 prope septa parum tenui-tunicatis sed non semper pallidioribus praeditae.

Notes: Most collections of M. leptospermi listed above had been assigned originally to M. mollis [auct., M. pulcherrima q.v.]. However, M. leptospermi has diminutive colonies up to 1 mm wide compared with up to 18 mm for M. pulcherrima: the latter also has abundant stomatopodia, very robust phialophores and larger ascospores and is apparently restricted to Syzygium cumini.
Meliolina leptospermi also differs from M. melaleucae: the latter has larger colonies (up to 5 mm) with stomatopodia, more robust phialophores, and somewhat larger ascospores with end cells which are as long as or usually slightly shorter than the central cells which show no thin-walled zones.
Two other species of Meliolina being recognized on Leptospermum are M. queenslandica on L. parvifolium and M. sarawacensis on L. javanicum. The former can be readily distinguished from M. leptospermi not only by its larger colonies (up to 4 mm) with abundant stomatopodia but also by the shape of its ascospores, with end cells shorter and narrower than the central cells. Meliolina sarawacensis has diminutive colonies (up to 1 mm) but its ascospores are shorter and wider and phialophores are longer and more frequently branched than those of M. leptospermi.
Drs B.G. Briggs and L.A.S. Johnson (in litt. to Dr K.A. Pirozynski) advised that Leptospermum ericoides should be included in the genus Kunzea.

Typification: New Zealand: Pureora, on 'L. scoparium', 21 Mar. 1963, S.J. Hughes (DAOM 159758, holotypus).