Biscogniauxia morphological characters


Description and illustration of characters

The stromatal surface may be plane to slightly convex and then with low margins to more or less concave or cupulate, and then with thick raised margins, B. marginata...).The stromata are considered carbonaceous when, sectionned with a razor blade, they turn out to be broken rather than properly cut.

The dehiscing outer layer is only seen on very young stromata, and therefore is rarely observed. It can be thin and torn up, operculum-like to crust-like.

Ostioles may be umbilicate or discoid when opening lower than stromatal surface, to papillate or coarsely papillate when opening higher than stromatal surface.

Perithecia may be obovoid to tubular, , but in some species this character may be variable within a same collection.

Ascospores may be one-celled to two-celled, ellipsoid to subglobose, with a germ slit that can be straight, sigmoid or bilateral. . The germ slit morphology is frequently a diagnostic character and its observation is made easier by the use of mounting media such as lactic acid or lactophenol which improve the clearness. Permanent mounts of ascospores in Polyvinylic alcohol (Rhodoviol®)* dissolved in lactophenol (Van Brummelen, 1967) make the germ slits particularly conspicuous. Bilateral germ slits are best observed on ascospores that are not exactly in front view, when focusing alternately on upper and lower side.

* Rhodoviol 50g, water 150g, lactic acid 80g, phenol 40g.