Summary:
Features include 1) growth on hardwood, most often alder, 2) a flat dark gray to dark brown fruitbody, the outer dehiscing layer dark brown and thin, 3) ostioles where perithecia open to the surface lower than the surface to slightly raised, and giving a punctate appearance, 4) spores that are elliptic, smooth, and dark brown, with a germ split the full length of the spore, 5) asci that are 8-spored with and apical ring turning blue in Melzer''s reagent, and 6) paraphyses.

Microscopic:
SPORES 17.5-22(25) x (8)9-11(12) microns, elliptic, "equilateral to slightly inequilateral, with narrowly rounded ends", smooth, dark brown, with straight germ slit spore-length, unicellular; ASCUS 180-200 x 11-13 microns, the spore-bearing part 145-160 microns long, stem 25-35 microns long, with apical ring turning blue in Melzer''s reagent, discoid, 2.5-3.5 microns high and 5.5-7 microns broad, (Rogers), SPORES 18-26 x 8-11 microns, very variable in size, elliptic-obtuse, dark brown when mature, uniseriate; ASCUS 8-spored, spore-producing part 120-130 x 10-14 microns, with short pedicel 15-20 microns long, cylindric; PARAPHYSES present, (Miller, J.H.)

Notes:
Biscogniauxia bartholomae has been found in WA, OR, and ID, (Miller, J.H.). Collections were examined from WA and BC (Rogers).

Synonyms and Alternate Names:
Merulius niveus Fr.
Plicatura alni Peck