Summary:
Features include minute grayish, tomentose-powdery, cylindric or cup-shaped fruitbodies crowded together on a grayish mat and microscopic characters including round spores, basidia, gelatinous context, clamp connections, and diverticulate hairs and crystals. Some authors call the epithet "poriiforme", based on Article 60.8 of the International Code of Botanical Nomenclature (2000) which appears to suggest that the compound should be corrected, but Thorn(4) provides the rationale that Article 60G.1(b) allows the compounding form "ae" to indicate the origin of the name, being a reference to the genus Poria rather than porus. Resupinatus poriaeformis has been recorded from BC, also AL, MD, MN, NC, NJ, SC, France, Germany, Sweden, New Zealand, according to Redhead who notes concerning the BC record, "Cooke (1957) has recorded this species from British Columbia. However, Donk (1962) was of the opinion that a number of taxa other than S. poriaeforme had been placed in synonymy by Cooke, e.g., S. incanum Kalchbr. and S. conspersum (Pers.) Donk. Until the collections examined by Cooke are rechecked, the exact identity of the one collection from British Columbia will not be known.". Redhead goes on to illustrate hyphal ends on the cup margin of a BC collection of this species in the sense of Donk, (see MICROSCOPIC). (Redhead(21)).

Odor:
indistinct (Buczacki)

Taste:
indistinct (Buczacki)

Microscopic:
spores 4.5-6 microns, round, smooth, inamyloid, colorless, thin-walled; basidia 4-spored, 20-30 x 5.5-6.5 microns, with basal clamp; cystidia absent; hyphae monomitic, hyphae of subiculum 2-3 microns wide, colorless, thin-walled, nodose-septate, with occasional branching; at apex of cupules "profusely branched and contorted dendrohyphidia", these from hyphae 2-2.5 microns wide, branches 1 micron wide or less, (Gilbertson), spores (4)5-7.5(8) x (1)3.5-4(5) microns, round to ovate, when strictly round 3.5-6 microns, more or less flattened on one side, smooth, colorless, apiculate; basidia 4-spored, 14-18 x 3.5-7 microns, clavate; walls of cups about 30-40 microns thick, the hymenium occupying a little less than half; "special hairs may form a palisade around margin of receptacle, 20-40 x 1-2.5 microns, straight to branched like dendrophyses", (Cooke(1)), hyphal ends on the cup margin (coralloid hairs) bear peculiar lecythiform branches with extremely slender necks, (Redhead(21)), spores (3.0)3.7-5.5 x (3.0)3.3-4.5 microns, nearly round or round, smooth, inamyloid, colorless; basidia 4-spored, (12)15-18(22) x 6-8 microns, broadly clavate or spheropedunculate, colorless; cystidia confined to rim of cup, 12-17 x 3.5-5.0 microns, clavate or fusoid, diverticulate, colorless; trama dark brown in KOH, densely interwoven, (10)20-30(50) microns deep including poorly defined subhymenium; gelatinous zone below trama proper, nearly colorless and continuous to base and forming a colorless gelatinous subiculum 20-50 microns thick; all hyphae including trama and cuticle, with clamps; cups externally clothed with colorless glossy hairs 1.5-3.0 (4.0) microns wide, "some with gelatinised walls, and inflated, others thin-walled, irregularly warted and lobed, with fine secretory pegs", coated with large (5-20 microns) "pale brown blocky crystals that in fact are masses of rhombic crystals 5-12 x 1-2 microns"; subiculum also covered with diverticulate hairs and crystalline material, (Thorn)

Spore Deposit:
white (Buczacki)

Notes:
R. poriaeforme is found in NC, Venezuela, South Africa, (Cooke(1)), ON, (Thorn, who gives distribution as widespread in Europe and North America and recorded in New Zealand, South Africa, and South America), AZ (Gilbertson), and QC, DE, GA, IA, LA, MA, ME, MO, NH, NY, OH, PA, VA, and WI, (Ginns).

Synonyms and Alternate Names:
Cudoniella aquatica (Lib.) Sacc.