Ceratostomella Sacc.

Ceratostomella Sacc., Michelia 1: 370. 1878. Xylomelasma Réblová, Mycologia 98: 87. 2006. Synonym. Lectotype species. Ceratostomella rostrata (Tode) Sacc., Syll. Fung. 1: 409. 1882 (Lectotype designated by Clements and Shear 1931). Description. Sexual morph. Ascomata perithecial, non-stromatic, venter globose to subglobose, superficial, semi-immersed or immersed, glabrous, roughened or tuberculate, dark brown to black, usually surrounded by sparse mycelium; hyphae growing out of the sides and bottom of the venter. Necks rostrate, central, cylindrical, straight to slightly flexuous, perpendicular or oblique to almost decumbent toward the substrate, sulcate or glabrous. Ostiolum periphysate. Ascomatal wall leathery to carbonaceous, two-layered. Outer layer consisting of brown, thick-walled cells, textura prismatica to textura angularis to textura epidermoidea, often with a distinct, external crustose layer of heavily pigmented, dark brown cells with opaque walls. Inner layer consisting of thinner-walled, subhyaline to hyaline, elongated and compressed cells. Ascogenous hyphae with croziers, with several lateral and terminal dehiscent cells produced sequentially and simultaneously, from each ascogenous cell one ascus arises as an outgrowth. Paraphyses abundant, unbranched, septate, hyaline, broad-celled and constricted at the septa, wider near the base, tapering, apically free, longer than the asci, disintegrating with age. Asci unitunicate, persistent, clavate to cylindrical-clavate, short-stipitate, truncate to broadly rounded at the apex, tapering toward the base from the sporiferous part, floating freely within the centrum at maturity, with a shallow, sometimes indistinct, non-amyloid apical annulus, 8 - spored. Ascus stipe usually contains non-refractive material deposited at the bottom part, visible after ascus dehiscence from the ascogenous cell. Ascospores variable in shape, suballantoid, ellipsoidal to irregularly ellipsoidal, globose or reniform, straight or curved, often flattened on one side, hyaline when young, becoming pale brown to brown before discharge from the ascus, aseptate, smooth, sometimes with indistinct terminal pores at one or both ends, arranged in a fascicle in the upper part of the ascus or 2–3 - seriate or uniseriate within the ascus. (Partially adopted from Réblová 2006.) Asexual morph. Hyphomycetous, dematiaceous; in culture only sterile mycelium was observed. Accepted species. Ceratostomella crypta, C. cuspidata, C. melanospora, C. novae-zelandiae, C. pyrenaica, C. rhynchophora, C. rostrata, and C. sordida. Notes. Species of Ceratostomella exhibit a variety of ascospore shapes, including suballantoid to reniform in C. cuspidata, suballantoid non-apiculate in C. rostrata, ellipsoidal slightly apiculate in C. crypta, C. melanospora, C. rhynchophora, and C. sordida, and ellipsoidal to oblong in C. pyrenaica. Réblová (2006) also described Ceratostomella sp. M. R. 2592, which has globose ascospores; however, this species lacks molecular data to confirm its placement in the genus. The key to identifying Ceratostomella species was provided by Réblová (2006). Table 3 displays morphological characteristics of Ceratostomella species accepted in the genus. * Size of ascomata (diam), asci and ascospores is given in µm. ** GF = GlobalFungi database; the number indicates the total number of samples with identical sequences detected in GlobalFungi. n / a = data not available. References: 1 = This study; 2 = Réblová 2006.