E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Also listed in Polypores category. Features include 1) resupinate growth on coniferous and hardwood structural timbers, 2) a whitish to buff to ochraceous gray finely pored surface that appears merulioid, this layer distinct from the thin, soft, buff subiculum, and rhizomorphs present, 3) spores that are broadly elliptic, smooth, dextrinoid, and pale brown, the inner spore layer cyanophilic, 4) a monomitic hyphal system, the hyphae with clamp connections. This species is an important cause of decay in houses and other wooden structures: masses of mycelium in walls and under floors give rise to coarse rhizomorphs that transport water from wet areas to structural wood far removed from the wet area.

Meruliporia incrassata has been found in BC, WA, OR, ID, NB, ON, AL, CA, CT, DC, FL, GA, IL, KY, LA, MI, MS, NC, NE, NY, OK, PA, SC, TN, TX, and VA, (Ginns(5)). It was not yet reported in Europe (Davidson, R.W.(1) 1953).

Fruiting body:
resupinate on wood over a wide area, soft when fresh, pores out to margin or almost to margin, easily separable; "pores" 2-3 per mm, appearing merulioid, thick-walled; whitish to buff to ochraceous gray; "tube layer" up to 0.6cm thick, distinct from subiculum; subiculum up to 0.7cm thick, soft-fibrous, buff, not zoned, (Gilbertson), annual, resupinate, 0.1-1.2cm thick, becoming 10-20cm or more long; spore-bearing surface poroid to merulioid in appearance, 2-4 round "tubes" per millimeter, 0.01-1cm deep, grayish brown to blackish, sometimes at first white; context separable from substrate, "whitish to cream or tan or light wood brown"; subiculum very thin, papery, peeling from the "tubes", whitish gray; rhizomorphs 0.3-1cm wide, "compressed, oval or round, extending from a source of water supply for great distances to the white, papery mycelial fans which cover large areas" and which, in favorable places, terminate in the fruitbody, (Cooke), fruitbody in type ''fragmentary, originally "effused for several inches, resupinate with the margin shortly reflexed, dirty white and slightly silky"; hymenium overgrown by an extraneous fungus, dark brown to blackish, hard, horny, the folds "forming minute, shallow brownish pores"; context now lacking, originally described as "substance thick, fleshy."'' (Ginns(17))

Microscopic:
SPORES 10-16 x 5-8 microns, broadly elliptic, rather variable in size and shape, smooth, dextrinoid, pale brown in KOH, spore print rusty brown; BASIDIA 4-spored, 30-60 x 7-9 microns, narrowly clavate; CYSTIDIA and other sterile hymenial elements absent; HYPHAE monomitic, subicular hyphae 2.5-9 microns wide, colorless in KOH, thin-walled, often branched, with simple septa and clamp connections, hyphae of trama 3.5-4.5 microns wide, colorless, parallel, thin-walled, with simple septa and clamp connections, (Gilbertson), SPORES 9-12 x 5-7 microns, ovate, somewhat flattened on one side, smooth, greenish to olive-brown or dark brown, walls 0.7-1 micron thick, in Melzer''s reagent brown with faint blue halo, in lacto-phenol cotton-blue, blue with no colored walls or contents visible, apiculate; BASIDIA 4-spored, 20-25 x 5-6 microns; hymenium simple, composed exclusively of basidia; CYSTIDIA not seen, CONTEXT formed of generative hyphae 2.5-5 microns wide, rather loosely interwoven to parallel-arranged, colorless, when old with yellowish coloring material on surface, more or less parallel with substrate, branching irregularly, with rare clamp connections, (Cooke), SPORES 9.6-13.6(16.8) x 5.6-8.0(8.8) microns, oval to broadly oval, adaxially flattened, smooth, dextrinoid (red-brown), pale yellow brown, rather thin-walled, the wall colorless in lactic-blue with a dark blue zone immediately inside; BASIDIA and CYSTIDIA not found; HYPHAE monomitic, tramal hyphae 3.2-4.8 microns wide, "parallel, closely packed, not readily separating even in squash mounts", colorless, thin-walled, septate with clamp connections, (Ginns(17))