Hysterobrevium mori

The fruit body is black, hard, generally 0.5-2 millimetres in length, much narrower than long, not taller than wide and with a fissure running along the length of the fruit body. The fruit bodies usually appear in large groups. Technically this type of fruit body is called a hysterothecium and hysterothecial fungi are ascomycetes. Hysterothecial fungi are fairly common but easily overlooked. Often you find them on hard, weathered wood in exposed habitats (e.g. on old wooden fence-posts, power poles or paling fences).

Hysterobrevium mori is a cosmopolitan species, previously long-known by the name Hysterographium mori.

Look-alikes

There are about a dozen genera in the families Hysteriaceae and Gloniaceae with such hysterothecia and identification of genera relies heavily on spore features.

The features of Hysterobrevium are: Spores colourless or brown and mostly shorter than 25 microns; the spores have both cross-wise and length-wise septa (3-9 of the former and 1-3 of the latter, generally along the central axis). Further spore features differentiate the species of the genus. 

Other hysterothecial genera on Canberra Nature Map

Gloniopsis

Hysterium

Oedohysterium