Summary:
This species in the strict sense of Ju(2) remains to be established for the Pacific Northwest. Features include 1) fruitbodies mainly on hardwood that are cushion-shaped to spread out flat, 2) color that is rusty to infrequently vinaceous, the surface flat or with conspicuous to inconspicuous perithecial prominences, 3) yellowish brown or brown granules immediately beneath the surface and between perithecia, with KOH-extractable pigments colored orange or rust, and 4) spores that are (8-) 9-12 x 4-5.5 microns, elliptic-inequilateral, with dehiscent perispore. |The species concept of Miller, J.H.(1) is wider than that of Ju(2): "Miller (1961) extended the definition of H. rubiginosum to cover those specimens with the ascospore size range 9-12.8 x 4-6 [microns], with stromata less than 3 mm thick, and with dark brown granules" [Latin name italicized bold], but Ju(2) restricted H. rubiginosum to "those specimens with yellowish brown to brown granules containing orange-series KOH-extractable pigments, with a rusty to infrequently vinaceous stromatal surface, with ellipsoid-inequilateral ascospores (8-) 9-12 x 4-5.5 microns, with dehiscent perispore, and without massive basal tissue", (Ju). |The synonyms given here are those given by Ju(2).

Microscopic:
SPORES (8)9-12 x 4-5.5 microns, elliptic-inequilateral, with narrowly rounded ends, "brown to dark brown, unicellular", "with straight germ slit spore-length", "perispore dehiscent in 10% KOH, smooth or with inconspicuous coil-like ornamentation", epispore smooth; ASCUS 100-170 x 5.5-8 microns, the spore-bearing part 63-83 microns long, the stem 35-90 microns long, with apical ring lightly blueing to blueing in Melzer''s reagent, discoid, 0.8-1.5 microns high and 2-3 microns broad; PERITHECIUM 200-500 microns in diameter and 300-600 microns high, spherical to obovoid, (Ju), SPORES 9-12.8 x 4-6 microns, inequilaterally elliptic, light to dark brown, obliquely uniseriate; ASCUS 60-80 x 8-9 microns in spore-bearing part, cylindric, with stem 40-50 microns long; PARAPHYSES copious, filiform; PERITHECIUM 200-500 microns in diameter and 300-700 microns high, hemispheric to oblong and angular from compression, (Miller, J.H.), SPORES 10-12 x 4.5-5.5 microns, broadly elliptic to bean-shaped, "rather flattened on one side, smooth, dark brown", with 1 droplet, germination cleft barely visible, spores uniseriate; ASCUS 8-spored, 120-130 x 5.5-8 microns, amyloid; PARAPHYSES barely visible, filiform, (Breitenbach)

Notes:
According to Miller, J.H.(1), Hypoxylon rubiginosum is found all over the world, not limited by thermal zones, and is the most common Hypoxylon species in the world and the most variable. Ju(2), who use the narrower concept, mention collections only from AZ, FL, GA, IL, MO, NJ, OH, SC, WI, France, Finland, Germany, Switzerland, and the United Kingdom. It has been reported at least from BC (Redhead(5), 1997, and Callan(1), 1998), but it is not certain whether these reports refer to collections fitting the narrower concept of Ju(2) or merely the wider concept of Miller, J.H.(1).

Synonyms and Alternate Names:
Endogone fasciculata Thaxt.
Endogone macrocarpa f. media Tul. & C. Tul.