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Summary: Features include 1) small size, 2) a spherical to irregular fruitbody with a surface that is white becoming rose (no yellow stage), the rose reaction intensified by KOH, 3) a spore mass that is white becoming olive, 4) absent columella, and 5) microscopic characters including narrowly elliptic spores from 6-spored basidia, and a peridium of appressed hyphae, in KOH the entire layer diffused with rose pigment. It is abundant among false truffles in the Pacific Northwest (Trappe(13)).
It is found from southern BC to northern California and the Rocky Mountains, (Trappe(13) who probably, like Trappe, M.(3) but unlike Smith, include Rhizopogon rubescens as a synonym). It is found in ID and also reported from BC and MI, according to Smith(4).
Outer Surface: 1-2cm across, "white when young, soon entirely rose color", (Smith(4)), 1-2cm across, spherical, flattened, or irregular; dingy rose color overall except in depressions where faintly buff-tinged; "unpolished and with scattered appressed rhizomorphs", (Smith(30))
Stem: columella absent (Smith(30))
Chemical Reactions: "FeSO4 no reaction on peridium or gleba; KOH intensifies the rose color", (Smith(30))
Interior: "white when young, slowly becoming olive", (Smith(30))
Microscopic: spores 6.5-8 x 2.8-3.2 microns, "peridium of appressed hyphae 4-10 microns wide, in KOH the entire layer diffused with rose pigment, as revived vinaceous brown", (Smith(4)), spores 6.5-8 x 2.8-3.2 microns, narrowly elliptic to oblong, in Melzer''s reagent yellowish individually and in groups, often falsely septate, in KOH colorless individually and in groups along the hymenium, thin-walled, "basal scar present but indistinct"; basidia 6-spored, 12-18 x 5-7 microns, subcylindric to clavate, colorless, thin-walled, and readily collapsing; paraphyses 10-20 x 6-11 microns, subspherical to ovoid or ellipsoid, "thin-walled, lacking a refractive body or granule"; cystidia none; subhymenium cellular; tramal plates of hyphae forming the central strand that are subparallel, colorless, thin-walled, smooth, nongelatinous, "lacking refractive globules or masses"; peridium of hyphae 4-10 microns wide, appressed, nongelatinous, "with incrustations and pigment deposits near the surface, the whole layer diffused with rose pigment (sections of fresh material mounted in KOH), no nests of enlarged cells seen", "as revived in KOH the layer vinaceous-brown and with much debris and incrusting material present"; all tissues inamyloid; clamp connections absent, (Smith(30))
Habitat / Range
in duff under Pinus contorta (Lodgepole Pine), July, (Smith(30))
Rhizopogon rubescens is honey yellow to yellow ocher at maturity (Smith(4)), but is regarded as a synonym of R. roseolus by multiple authors. Rhizopogon albiroseus has a surface that is dull white to brownish at maturity (Smith(4)). Rhizopogon abietis becomes yellow (Smith(4)). Rhizopogon ventricosporus is ocher-yellow (Smith(4)). Rhizopogon pseudoroseolus has larger, subfusoid spores and gives a strong reaction in FeSO4, (Smith(30)).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2020. E-Flora BC:
Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for
Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2021-10-22 12:48:27 AM
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