Hercospora tiliae  

Description contributed by Graham Kinsey (CABI), based also on Sutton (1980).

Anamorph: Rabenhorstia tiliae (Fr.) Fr. (1849). Conidiomata to 1300 µm diam, stromatic, immersed beneath periderm layers, applanate and erumpent in the central portion, the wall dark brown, composed of thick-walled textura intricata above and at the sides and pale brown textura angularis below, with a cap-like structure composed of textura oblita that breaks away to expose the irregular dehiscent area. Conidiophores to 90µm in length and 3-4 µm diam, branched especially at the base, hyaline, septate, smooth, developing in a mucilaginous layer, formed at the base and sides of the conidiomata wall. Conidiogenous cells terminal or intercalary with loci immeditaely below septa, straight or curved, apparently not proliferating. Conidia 18-20 x 6-7.5 µm, ellipsoidal to cylindric-ellipsoidal, hyaline, smooth, aseptate, thick-walled, the base sometimes truncate, formed in mucilage but without a gelatinous sheath or appendages.

Teleomorph: stromata appearing as conical pustules 700-800 µm diam, erumpent through the host bark, composed of interwoven hyphae, with a greyish cushion-shaped ectostromatic disc through which the perithecial necks emerge, entostroma whitish and intermixed with host bark cells, each stroma entirely surrounded by a black zone line composed of densely packed cells within the host bark, scattered, containing a cluster of 2-10 ascomata. Ascomata 200-400 µm diam, perithecial, ± globose, with a long black oblique neck, the necks converging and often united and forming a single large opening, scarcely exceeding the stromatal surface. Interascal tissue absent, but necks periphysate. Asci 75-100 x 9-12 µm, broadly clavate to cylindrical, short-stalked, 8-spored, possibly with an apical apparatus, 8-spored. Ascospores 12-18 x 6-8 µm, ellipsoidal to cylindrical, hyaline, smooth, 1-septate, not or scarcely constricted at the septum.