Melanomma
Unlichenized fungi that grow as part of epiphytic crustose communities; thallus white scurfy, sometimes conspicuous and well delimited; perithecia partly sunken in the thallus, jet black, hemispheric; perithecial wall formed of dark brown-pigmented, closely entwined hyphae, the wall continuous below the asci; hymenium formed of thin, densely branched and anastomosing paraphysis-like hyphae; asci cylindric to narrowly clavate, thin-walled, IKI-; spores 8 per ascus, brown at maturity, surrounded by a thick gelatinous sheath; more or less elliptic, 3-septate, strongly constricted around the central septum, the two halves sometimes of uneven size.
References: Harris (1973).
Melanomma polita Björk ined.
Thallus prominent, white and scurfy, often with a slightly darker prothallus, lacking algae or algae sparse, abundant calcium oxalate crystals throughout; perithecia black, emerging from below the thallus, only about half of the perithecial wall visible from above, the exposed part black and distinctly glossy; paraphyses dense, thin, tangled, branching and anastomosing, especially over the asci; asci cylindrical 80-100 µ high, with 8 spores haphazardly stacked; spores 3-septate, rarely with more septae, constricted at the central septum, 15-25 × 5.5-9 µ, medium gold-brown, darker brown or red in K, with a gelatinous perispore visible at least in K.
Reactions: Spot tests all negative.
Contents: Unknown, but probably no lichen substances.
Habitat: On smooth bark of Populus tremuloides trunks and branches, in open, moderately dry forests. Lower elevations.
Similar Species: Arthonia patellulata and Lecania dubitans appear similar and are also common on smooth Populus tremuloides bark, and M. polita often grow intermixed with these; Melanomma polita is easily distinguished by its brighter white thallus and sunken perithecia.
Specimens: Goward 80-18-1.
Local Status: Common.
Notes: Harris (1973) provides discussion of an undescribed Melanomma on Populus tremuloides bark in eastern North America; this seems not to be the same as M. polita, having clavate or clavate-cylindric asci 60-80 µ long. Melanomma polita is known from inland BC and the Yukon.