Mycomicrothelia minutissima (C.Knight) D.Hawksw.
*Account prepared by Dr D.L. Hawksworth (C.M.I. Kew, Surrey).
Verrucaria minutissima Knight, T.N.Z.I. 8: 324 (1876), tab. 10, fig. 20.
Holotype: New Zealand. Near Wellington. Charles Knight, Herb. Knight vol. 58, p. 15, WELT!
Thallus dark grey-brown, very thin, plicate-rugose to ± irregularly cracked, forming dark, irregular patches, 3-5 cm diam., on bark. Ascomata arising singly but commonly 2-3-confluent, scattered, immersed, the upper layers of bark raised to form low hemispherical projections, individual ascomata dimidiate, 200-300 µm diam., to 150 µm tall, black basal fringe usually poorly delimited but extending to c. 125 µm in some fruits, ostiole depressed, centrum visible as a white spot, gaping, 40-50 µm diam., involucrellum dark reddish-brown, unchanged in K, 20-30 µm thick, consisting of host cells intermixed with fungal hyphae. Pseudoparaphyses cellular, abundant, persistent, filiform, branched and anastomosing, septate, 1.5-2 µm thick. Asci arising from base of ascomatal cavity, oriented towards ostiole, elongate-clavate to subcylindrical, short-stalked, with a distinct, internal apical beak when young, 65-75 × 12-14 µm, 8-spored. Ascospores biseriate, ellipsoid to soleiform, 1-septate, slightly constricted at septum, lower cell somewhat shorter and narrower, apex rounded, base rounded to subattenuate, pale olivaceous-brown, verruculose without a distinct gelatinous sheath, 17-22(-24) × 5.5-7.5 µm.
Endemic
Known only from the type collection.
