Details about map content are available here Click on the map dots to view record details.
Species Information
Summary: Features include 1) a pallid surface that becomes dingy vinaceous and areolate [cracked like dried mud] or warted, and often dries with a cinnamon undertone, 2) an olivaceous spore mass with small chambers that dries dull ochraceous, 3) growth under Douglas-fir, 4) a dark olive reaction of the dried surface to FeSO4, 5) a vinaceous to black reaction of surface to KOH, and 6) microscopic characters including narrowly oblong smooth spores from 6-spored and 8-spored basidia, and a peridial epicutis that is a collapsed trichodermium with end-cells 8-15 microns wide and clavate to cystidioid. It is abundant in the Pacific Northwest (Trappe(13)).
Rhizopogon subareolatus has been found from southwestern BC to northern CA and east to CO, (Trappe(13)). The holotype collection is from OR (Smith(30)). It was reported from WA by Colgan(2). There is a Paul Kroeger collection from BC deposited at the University of British Columbia.
Outer Surface: 1-6cm across, pallid at first, "becoming dingy vinaceous and as dried dark dingy yellow-brown (rarely with bluish dark gray areas)"; dry and unpolished, becoming areolate [cracked like dried mud], (Smith(4)), 1-6cm across, spherical to nearly spherical; "pallid at first and becoming dingy vinaceous, when dried with dark dingy yellow-brown or rarely with bluish fuscous areas, often with an obscure ochraceous under tone", (J. Trappe''s collections placed here "were white, slowly becoming umber brown"); dry and unpolished, the surface "becoming separated into minute areolae or small warts", (Smith(30)), "Thin, dark reddish brown to grayish brown surface underlain by a whitish, pink-staining layer", "prominent dark brown rhizomorphs at base and sides", (Trappe, M.(3))
Chemical Reactions: surface "with FeSO4 dark olive, in KOH inky black in old ones, when young staining vinaceous", (Smith(4)), "dark olive in FeSO4 (on dried peridium), in KOH inky black on old specimen, vinaceous on young ones, with olive areas in the subcutis as revived in KOH", (Smith(30))
Interior: olivaceous drying ochraceous, (Smith(4)), "when dried firm and easy to section"; "pallid to olivaceous, drying dull ochraceous"; chambers small, (Smith(30)), olive brown to brown (Trappe, M.(3))
Odor: none, but in J. Trappe''s collections placed here "apparently also distinctive but variable, according to Trappe resembling fresh frankfurters, fermenting molasses, or merely pungent-fruity", (Smith(30)), mild to garlicky-pungent (Trappe, M.(3))
Taste: mild to garlicky-pungent (Trappe, M.(3))
Microscopic: spores 6-7 x 2-2.3 microns, end cells of epicuticular hyphae "8-15 microns wide and clavate to cystidioid", "flagellate hyphal ends absent", (Smith(4)), spores 6-7 x 2-2.3 microns, narrowly oblong, smooth, in Melzer''s reagent yellowish-transparent singly, deeper yellowish in masses, in KOH colorless singly, dingy yellow-brown in groups, basal scar indistinct; basidia 6-spored and 8-spored, clavate, colorless, readily collapsing; paraphyses 5-10(12) microns wide, colorless in KOH, thin-walled to having wall slightly thickened when old; "subhymenium inconspicuous, of narrow basal cells at bottom of hymenium"; tramal plates "of refractive interwoven hyphae lacking colored contents and wall incrustations"; peridial inner layer of smooth to incrusted, colorless to brown hyphae "with much of the area green in KOH, amorphous dark brown to fuscous pigment pockets and incrustations copious throughout the layer", no sphaerocysts seen but some cells up to 20 microns in diameter, "oleiferous hyphae not uncommon"; peridial epicutis "in the form of a collapsed trichodermium of hyphae with rusty yellow-brown walls in KOH", the cells 8-15 microns in diameter and short, "the end-cells clavate to cystidioid, walls smooth to encrusted, no flagellate hyphal cells observed, areas of dark green in the layer as revived in KOH"; all hyphae inamyloid but amyloid particles scattered along some hyphae; clamp connections none, (Smith(30)), peridial subcutis has a characteristic red layer revived in KOH (use 25X objective), although this fades after about 5 years of dried storage to pale pink and may disappear entirely after 7-10 years, (NATS)
Habitat / Range
type collection in duff under pine, during fall rainy season, (Smith(30)), associated with Pseudotsuga (Douglas-fir); fruiting year-round, (Trappe, M.(3)), mycorrhizal host in the Pacific Northwest Pseudotsuga (Trappe(13))
Similar Species
Rhizopogon hawkerae and Rhizopogon villosulus are similar Douglas-fir associated species that also have woven brown walled hyphae in the peridium revived in KOH: the former has spores 6.5-8 x 2.2-2.8 microns and occasional to abundant flagellate hyphae, and the latter lacks a red layer in the subcutis revived in KOH (may be orangish brown), whereas R. subareolatus has spores 6-7 x 2-2.3 microns, no flagellate hyphae, and subcutis with a red layer revived in KOH, (NATS). Beside those two, other species associated with Douglas-fir that have woven brown hyphae in the peridium revived in KOH include Rhizopogon parksii, Rhizopogon villescens, Rhizopogon zelleri, (all with at least some flagellate hyphae), Rhizopogon vinicolor (spores 5.5-8 x 3-4.5 microns), and Rhizopogon subclavatisporus (spores 8-13 x 4.5-7 microns and thicker on one end), (NATS). See also SIMILAR section of Rhizopogon rudus and Rhizopogon subclavitisporus.
