Summary:
Features include 1) growth on coniferous branches, 2) fruitbodies that are erumpent, small, composed of single perithecia or 3-12 coalesced, with a superficial, light gray-brown carbonous surface and white fleshy-leathery inside, the surface cracked, uneven from prominently projecting perithecia, 3) spores that are very variable in shape, widely elliptic and fusoid to elliptic-oblong, (young spores with a colorless sheath), dark brown to almost opaque, diagonally uniseriate or uniseriate in asci, with paraphyses present. It was considered to be a Rosellinia by Petrini and Mueller (1986), but the taxonomic position is uncertain, (Ju).

Microscopic:
SPORES 20-36 x 12-18 microns, very variable in shape, widely elliptic and fusoid to elliptic-oblong, inequilaterally elliptic with obtuse ends, young spores with colorless sheath (readily dissolving from mature spores), thickened at ends, 1.5 microns at sides and 2-3 microns at ends, dark brown to almost opaque, diagonally uniseriate or uniseriate; ASCUS 180-210 x 18 microns in spore-bearing part, cylindric, pedicel [stem] 20-40 microns long; PARAPHYSES present; PERITHECIUM 700-1000 microns in diameter, hemispheric, (Miller, J.H.)

Notes:
Hypoxylon diathrauston has been reported from BC (Redhead(5)). It has been found in OR, ID, CA, CO, MT, Switzerland, (Miller, J.H.)