Xylariaceae morphological characters


Description and illustration of characters

This page illustrates the characters considered in the dichotomous and synoptic keys to xylariaceous genera. They are ordered following the synoptic key organization. Links to illustrative photographs are in blue. It is also possible to open illustrative plates by clicking "illustration" (just above) or by clicking the subtitles below.

Stromata and ascomata

Stromata may be bipartite. In this case the upper layer that hides the stromatal surface disappears at maturity. This character can be guessed from remnants at margins, even at maturity. It is encountered in Biscogniauxia and Obolarina.

Stromata may be more or less immersed in substrate (some Anthostomella, Euepixylon) erumpent (Entoleuca), superficial broadly attached (most cases), superficial loosely attached (Kretzschmaria), constricted at base (Daldinia) or stipitate (Xylaria). In most genera, the stromatal tissue is homogenous. It is hollow and filled with liquid in Entonaema and presents concentric zones in Daldinia.

Stromata are most often multiperitheciate and perithecia arranged in one layer. In Lopadostoma subgenus Lopadostoma, perithecia are in valsoid configuration. Uniperitheciate stromata occur in Anthostomella,Creosphaeria, Hypocopra, Lopadostoma subgenus Anthostomopsis, Nemania and Rosellinia, frequently with a tendency to become coalescent.

Acsi and ascospores

At the generic level, the most distinctive feature of asci lies in the apical apparatus. It may be broader than high (ring-like or discoid) or higher than broad (inverted hat-shaped to urn-shaped), easily seen when bluing in Melzer's reagent (amyloid). Amyloidity is not constant within a genus and is helpful at the specific level.

Ascospores are typically one-celled, ellipsoid, provided with a germination site and pigmented. Biscogniauxia anceps is noteworthy in having two-celled ascospores that frequently remains hyaline, even when mature. In most Anthostomella taxa, young ascospores are conspicuously two-celled and keep a dwarf hyaline cell when mature. This also occurs in Nemania, Rosellinia and Xylaria, but much less conspicuously.

The germination site is slit-like (sigmoid or bilateral at times), except in Euepixylon where it is pore-like. The shape, the relative length of the germ slit and its position on the ascospore's wall is often diagnostic at the specific level.

In Daldinia and Hypoxylon the perispore may be dehiscent in 10% KOH. Unfortunately this character is not constant in all taxa and does not allow a reliable distinction of these two genera.