Hysterium angustatum

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).

Hysterium angustatum is a cosmopolitan species.

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 spores are elongated and have septa (or cross walls), either only transverse septa (across the width of the spore) or also with longitudinal septa (at right angles to the transverse septa).

The features of Hysterium are: Pigment is present in the spores; the spores have only cross-wise septa, commonly 3 but there may be more and the medial cells in the spores are not swollen. Further spore features differentiate the species of the genus. 

Other hysterothecial genera on Canberra Nature Map

Gloniopsis

Hysterobrevium

Oedohysterium