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Page number:258 
Remarks (public):Habitat: Common in eastern North America on the bark of standing Ostrya virginiana and Quercus alba; less common on the bark of other deciduous trees. The fungus has been collected in Ontario on fallen logs of Acer saccharum. Normally, however, Aleurodiscus oakesii occurs on living trees. According to Tehon and Jacks (1933), the fungus is responsible for the unsightly 'smooth-patch' disease of Quercus alba in Illinois. I have observed the fungus in Ontario associated with a similar sloughing-off of the outer bark of living Acer saccharum. Further study is necessary to determine if the fungus, under certain conditions, does invade living tissue. Lair (1946) discusses in detail a 'smooth-patch' condition of white oaks, which in North Carolina is apparently caused by Corticium maculare Lair. Lair, in studies involving bark block cultures of A. oakesii, further reports that the mycelium of A. oakesii, even in 11-month-old cultures, was restricted to the surface of the blocks.
Aleurodiscus oakesii is an amyloid-spored and dimitic fungus with skeletal pseudocystidia. Those who adhere to a strict interpretation of basidiomycetes based on hyphal systems would probably remove this species from the typically monomitic Aleurodiscus. Since the species is dimitic, it might be regarded as a large-spored Stereum Hill per Gray. The spores, however, are roughened and too large for a Stereum. Furthermore, the dimitic system represented here is marginal, with skeletal hyphae scattered in the lower context and forming the abhymenium.
The moniliform-constricted elements found in this species are of a skeletal origin, and are not fundamentally different from `pseudocystidia' (sensu Lentz (1955)) found in several Sterea. These skeletal pseudocystidia are also homologous with the generative pseudocystidia encountered in most of the Aleurodisci.
 
Description type:Non-original description 
Description:Aleurodiscus oakesii (Berk. et Curt.) Höhn. et Litsch., K. Akad. Wiss. Wien Math.-Nat. Kl. Sitzungsb. 116: 802. 1907. (Fig. 15) - Corticium oakesii Berk. et Curt., Grev. 1: 166. 1873.
[Aleurodiscus oakesii (Berk. et Curt.) Cooke, Grev. 3: 172. 1875(nomen generica nudum).]
Basidiocarp initially disciform to cyphelloid, 1.5-5.5 mm in diameter, gregarious to confluent, forming irregular, substereoid patches; margins reflexed to inrolled on drying. Fructification 500-600 µm thick in cross section; texture farinose-pulverulent to subcoriaceous. Hymenial surface concave, continuous; drying avellaneous to ochraceous-buff colored with cinereous tints. Abhymenial surface floccose, white when fresh; drying pallid, subglabrous to striate. Content dimitic, generative hyphae branched, simpleseptate, 3-3.5 µm in diameter, thin-walled to partially thick-walled; skeletal hyphae, mostly basal, unbranched, aseptate, thick-walled, measuring up to 4.5 µm in diameter. Catahymenium composed of numerous acanthophyses, skeletal pseudocystidia, simple paraphysoids, and basidial elements. Acanthophyses filiform to subclavate, 60-80 x 4-6 µm; walls thin to slightly thickened, bearing scattered acicular prongs either laterally or apically or both. Acanthophyses hyaline in KOH; individual prongs measuring mostly 5-8 x 1 µm. Pseudocystidia ampulliform to moniliform-cylindric, 4.5-6(-8) µm in diameter, mostly embedded, thick-walled, arising from thick-walled, aseptate hyphae; contents not darkening in sulphobenzaldehyde. Paraphysoids simple, 3-3.5 µm in diameter, with partially thickened walls. Basidioles clavate, 60-100 x 12-16(-18) µm; frequently bearing scattered acicular prongs. Basidia emergent at maturity, flexuous-subclavate, 75-120 x 12-15.5(-20) µm; bearing (two) four divergent, fleshy sterigmata 13-25 µm long and up to 5.5 µm wide at base. Basidiospores ovoid-ellipsoid, (16-)18-25(-27) x (10-)12-14(-17) µm, apiculate, flattened adaxially, walls thickened up to 2.3 µm at maturity, and then bearing opposite germ-pores at each pole; walls smooth to roughened in KOH, distinctly echinate in Melzer's, amyloid.
Distribution: Ontario, Quebec, Nova Scotia; New England to Alabama and Mississippi, westward to Iowa, Missouri, Minnesota, Nebraska, and Wisconsin; Great Britain; China; Japan. A single collection reported by Viégas (1945, p. 255) from Brazil appears to be Aleurodiscus mirabilis (Berk. et Curt.) Höhn.



 
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