Summary:
Features include 1) a spherical to nearly spherical fruitbody with the surface cinnamon becoming dark brown then blackish, 2) a spore mass that is dark brown, 3) growth under conifers, 4) chemical characters including the cut peridium staining red with KOH, and 5) microscopic characters including elliptic to narrowly ovoid spores from 4-spored and 6-spored basidia and a peridium of appressed interwoven hyphae that is reddish in KOH.

Chemical Reactions:
cut peridium when fresh staining red with KOH, soon dark olive-fuscous with FeSO4, (Smith(4)), KOH staining cut peridium red, FeSO4 slowly becoming dark olive-fuscous, (Harrison)

Interior:
dark brown and tough but sectioning easily when dried, (Smith), tough, cavities large for genus, sectioning easily (not bone hard); very dark brown, when dried olivaceous, (Harrison)

Microscopic:
spores 7-9 x 3-4 microns, yellowish singly in KOH; subhymenial hyphae filamentous, peridium of appressed interwoven hyphae (3)4-10(14) microns wide, the layer reddish in KOH, (Smith), spores 7-9 x 3-4 microns, elliptic to narrowly ovoid, smooth, "base obscurely truncate in some (not at all so in most)", in Melzer''s reagent ochraceous-cinnamon, in KOH yellowish singly but cinnamon in masses, wall up to 0.25 microns thick; basidia 4-spored and 6-spored, 7-10 microns wide, clavate, sterigmata 1-1.5 microns long; cystidia 12-18 microns in widest part, clavate, colorless, thin-walled, "empty"; brachybasidioles oval to elliptic "with a refractive central body which merely stains yellowish in KOH, usually in the form of a terminal cell of a 2- to 3-celled filament with all the cells having the same features as the end cell"; subhymenium "of filamentous highly refractive hyphae as branches from tramal plate hyphae"; tramal plates with hyphae 2-4 microns wide, that are refractive-gelatinous, smooth, and colorless in KOH; peridium of hyphae (3)4-10(14) microns wide, appressed-interwoven, "some cells inflated, walls thin but often with adhering debris, the layer (including the debris) reddish to reddish cinnamon in KOH"; clamp connections none, (Harrison)

Notes:
Rhizopogon cinnamomeus was described from BC.

Synonyms and Alternate Names:
Corticium areolatum Bres.
Corticium udicola Bourdot