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

Summary:
Features include a disc-shaped to cup-like, brownish fruitbody, growth on hardwood especially birch, and microscopic characters. Klett(2) restricted Exidia repanda to the narrow spored form 11-15 x (2.5)3-4 microns examined from AK, Sweden, and Germany, and distributed "Probably throughout Alaska, northern Canada, and northern Europe", and had not seen any North American collections of the wider spored form (12-16.5 x 4-6 microns) which is supposed to occur sporadically in middle and western Europe.

Exidia repanda has been reported from AK (Klett), WA, ID, ON, AL, LA, ME, MN, and NJ, (Ginns), and France, Germany, Poland, Sweden, USSR, and Japan, (Aoki). There is a BC collection from 1965 by J. Holms at the University of British Columbia and another BC collection from 1969 by Robert Gilbertson at the University of Arizona.

Fruiting body:
up to 2.5cm broad, disc-shaped, becoming pezizoid (cup-like), appressed, centrally attached, with thick margins, not readily anastomosing; "at first brownish hyaline, then brownish flesh-colored, finally cinnamon-brown, more or less smoky or olivaceous"; spore bearing surface smooth to furrowed or wrinkled, (Martin), 1-2.5cm and 0.2-0.5cm thick, round, flat, button-like, closely appressed to substrate, attached only at central point, gelatinous; light brown or brown; with smooth surface or surface covered with sparse ribs, (Raitviir), up to 1cm across, 0.3cm thick, at first pustulate, becoming disc-shaped, centrally attached by a point, remaining separate or anastomosing, "but a contact line remaining in the latter case"; tan to yellowish brown, golden brown, cinnamon or mustard brown; surface flat to undulating or slightly ridged, smooth, occasionally with sparse fine warts; underside smooth, flat, appressed to the substrate, colored as upper surface, occasionally with brown dots; margins "usually thick, rounded to wavy, occasionally thin and appressed"; dried fruitbodies thin, horny, dark brown, (Aoki), "at first pustulate, expanding, becoming discoid", 1-2.5cm in diameter and up to 0.5cm thick, centrally attached by a point, remaining discrete or anastomosing with neighboring fruitbodies but retaining individuality; at first brownish hyaline, becoming yellowish brown to golden brown to cinnamon to olivaceous grayish brown; outer surface flat to undulate to slightly ridged, smooth to occasionally finely asperulate; undersurface sterile, smooth, flat, colored as outer surface or slightly lighter, "free at the point of attachment, appressed to the substratum towards the margins", margins thick, scalloped, (Klett), spore deposit white (Buczacki)

Microscopic:
spores mostly 12-13 x 3-4 microns, allantoid [curved sausage-shaped]; probasidia 10-13(16) x 9-11(13) microns, ovate to nearly spherical, brownish, becoming cruciate-septate or sometimes merely 2-celled, epibasidia slender, 2-2.5 microns wide below the expanded tips, up to 50 microns long, (Martin), spores 8.5-17 x 2-4 microns, oblong-elliptic to reniform or allantoid, with broad (about 1 micron) apiculus, colorless, aseptate before germination, germination by conidial formation or germ tube; basidia in cymose clusters, probasidia 8-17 x 4.5-9.5 microns, at first subcylindric to clavate, becoming predominantly subspherical or obovate, some spherical or ellipsoid, with or without short stem, with basal clamp connections, 2-4-celled by longitudinal to slightly oblique septa, hypobasidia 9-17.5 x 6-10 microns, differentiating 2-4 segments, epibasidia cylindric, up to 45 microns long, 1-2.5 microns wide at broadest point, somewhat contorted; dikaryophyses forming a layer 35-65 microns thick above the basidial zone, "contorted, irregularly branched, and branches tapering toward the pointed apices", with basal clamp connections; hyphae 1-4 microns thick, thin-walled, with conspicuous clamp connections, (Aoki), spores 11-15 x (2.5)3-4 microns, cylindric-curved, colorless, white in mass, capable of germinating by repetition; basidia "arising as clavate structures subtended by clamp connections, proliferating through the clamp connections to form cymose clusters", probasidia becoming ellipsoid to obovate, then 10-15 x 7.5-10.5 microns, becoming 2-celled to 4-celled by longitudinal to slightly oblique septa, hypobasidia mostly ellipsoid, 11-15 x 8-11 microns, epibasidia 1.5-2.5 microns wide at bases; dikaryophyses with basal clamp connections, forming a layer 10-40 microns thick above the level of the basidia, mostly 2-3.5 microns wide toward bases, contorted, irregularly branched apically, with occasional ones cylindric, up to 5 microns wide, contorted, unbranched, or abruptly narrowed apically and branched; hyphae 1.5-3.5 microns wide, thin-walled, "with conspicuous clamp connections varying from closed to keyhole to looplike, occasionally spurred", (Klett)