Nemania morphological characters


Description and illustration of characters

Stromata are usually multiperitheciate and superficial, less frequently uniperitheciate and then more or less immersed in wood. It is not rare to observe some uniperitheciate stromata at margins of multiperitheciate stromata, while uniperitheciate stromata often show a tendency to fuse in small groups.

Stromata vary in degree of carbonization of the surface layer, interperithecial tissue and perithecial wall. In the following keys and descriptions, they are considered to be weakly carbonaceous when they can be properly sectionned with a razor blade; when carbonaceous, they are rather broken by the razor blade, with a characteristic noise.

Stromatal surface may have conspicuous perithecial mounds or inconspicuous perithecial mounds .

Whitish interperithecial tissue is usually present in young stromata, becomes grey to grey brown with age and finally disappears. It is absent from carbonaceous stromata, or very inconspicuous. The tissue beneath the perithecial layer (basal tissue) is distinctive when white, massive and persisting in mature stromata .

Ostioles of Nemania taxa are always papillate, opening higher than the stromatal surface. They may be minutely papillate to coarsely papillate, but this character may vary within a same taxon.

Asci may be short-stipitate , with the stipe much shorter than the spore-bearing part, rarely more than half the spore-bearing part length, to long-stipitate , with the stipe nearly as long as the spore-bearing part.

Apical apparatus may be amyloid (blueing in Melzer's reagent) . It is considered to be dextrinoid when it turns pale red brown (in Lugol's solution). It is usually higher than broad but sometimes as broad as high (cuboid). Its shape may vary from cylindrical when its diameter is constant to inverted hat-shaped when it is broader and flattened at apex, or urn-shaped, when rounded in lower part.

Ascospores are pale to medium brown in most species, dark brown in a few cases . Their colour varies with the mounting medium used for their observation, therefore it must be evaluated in water. A hyaline sheath enclosing each ascospore is more conspicuous when observed in Indian ink . In one species , the ascospore wall is longitudinally striate while it is smooth in all other European species. Ascospores may have beaked ends or pinched ends but these features are usually not diagnostic, and likewise are observed in other genera (Rosellinia, Xylaria). Immature ascospores bear at their lower end a very inconspicuous and fugacious hyaline cellular appendage,and this end is frequently slightly truncate at maturity.

Germ slits. The shape, length and location of the ascospore germ slit are often diagnostic in Nemania. The germ slit is considered conspicuous when easily seen in water, Melzer's reagent or 3% KOH at a magnification x 1000 in all ascospores observed in front view, fairly conspicuous when seen in only a few percentage of ascospores, and inconspicuous when apparently absent when observed in these media. The germ slit becomes much more conspicuous when permanent mounts of ascospores are made in Polyvinyl alcohol (Rhodoviol®) dissolved in Lactophenol * (PVAL) (Van Brummelen, 1967), but in that medium, ascospores are paler and occasionally become somewhat bulged. In Nemania, the germ slit is usually on the less convex side but may be on the more convex side in some species.

In "Hypoxylon terricola", a species presented herein with Nemania, ascospores are enclosed in a gelatinous sheath that needs to be observed in diluted Indian ink (Indian ink: 1, water: 1).

Photographs of ascospores were taken from permanent mounts in PVAL, photographs of asci and their apical apparatus were taken from permanent mounts in 50% Glycerol-50% Lugol's solution.

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