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

Summary:
Features include 1) a viscid to glutinous, appendiculate cap that is whitish to orange-cinnamon to reddish brown or dark brown and may turn more vinaceous or brownish when bruised, 2) white to yellowish flesh, 3) angular, yellow to pale ochraceous pores that darken (but do not change when bruised), 4) a white stem that becomes yellow at the top and stains darker when bruised or old, 5) glandular dots on the stem that may be rare or scattered, 6) a white to purplish brown or reddish brown membranous (not gelatinous) veil that stains vinaceous gray and that leaves remnants on the cap and sometimes an annular zone on stem, and 7) growth under conifers especially pines. Nguyen(3) provide molecular and other evidence to show that Suillus borealis is a synonym of Suillus brunnescens. Because considerable extra information is contained in the S. borealis descriptions, those are included too.

Suillus brunnescens is found at in least OR, ID, CO, and CA, (Bessette). The distribution is extended by including S. borealis. As Suillus borealis, S. brunnescens is found in the northern Rocky Mountains and the Pacific Northwest (Bessette), ID (Smith(36)), northern CA (rare - Thiers), WA (Buck McAdoo, Eugene Butler, pers. comm.), OR (Oregon State University Herbarium), and BC (Michael Beug, pers. comm.).

Cap:
4.5-15cm, convex becoming nearly flat when old; "white at first, changing to yellow-brown or dark brown to lilac-brown as the gluten darkens, staining vinaceous, then brownish when bruised"; "glutinous to viscid, often streaked", bald; margin appendiculate [with hanging veil remnants] when young, becoming even when old, (Bessette), 4-15cm, convex to nearly flat; at first white, the gluten soon changing to chocolate color but often showing a lilac brown tone while darkening; glutinous to viscid, often appearing streaked from the gluten, (Smith), 5-11.5cm, convex, becoming broadly convex to nearly flat, sometimes depressed when old; orange-cinnamon to reddish brown or dark brown, not changing when bruised; viscid to glutinous, often streaked, bald; margin appendiculate [with hanging veil remnants], (Bessette for S. borealis), 4-12(15)cm, convex becoming broadly convex to nearly flat; whitish in buried buttons but color soon changing to light to dark dull vinaceous-brown or reddish chocolate color; bald, glutinous; margin "at first decorated with remnants of a false veil of dry cottony tissue except for the outer layer which is white when the cap is white but soon changes through vinaceous buff to army brown or more chocolate color and finally gelatinizes before the veil is obliterated entirely, typically forming a continuous band (not breaking into denticulate patches)", (Smith for S. borealis), brown, sometimes dark brown on the disc, fading to pale brown on the margin, (Thiers for S. borealis)

Flesh:
white at first, becoming yellowish throughout or at least at the top of the stem and near the tubes, unchanging when exposed, (Bessette), thick; white when young, becoming yellow in top of stem and along tubes or finally yellowish throughout, not staining when cut or bruised, (Smith), whitish at first, becoming yellow when mature, (Bessette), "white then becoming slowly bright yellow especially above the tubes"; in stem "white, then slowly yellow (especially in cortex)" and in the base where damaged by larvae "often orange-ochraceous to vinaceous-red", (Smith for S. borealis), 1-2cm thick, whitish when young, becoming yellow when old, changing to yellow when exposed in young fruitbodies, in stem white to yellow and unchanging when exposed, (Thiers for S. borealis)

Pores:
2-3 per mm, angular to irregular; pale ochraceous at first, darkening when old, unchanging when bruised; tube layer 0.6-1.3cm thick, adnate to subdecurrent, (Bessette), about 2 per mm, pale ochraceous and not staining when bruised; tube layer up to 1.5cm thick in large caps (mostly less than 1cm thick), adnate to decurrent, pale ochraceous, (Smith), 1-2 per mm, angular, "pale yellow at first, darkening to yellow and finally dull golden yellow" when mature, not staining when bruised; tube layer 0.6-1cm thick, depressed near stem when old, (Bessette for S. borealis), 1-2 per mm, round to angular; "pale dull yellow and not staining when bruised or only slightly brownish overnight, in age often grayish"; tube layer 0.4-0.7cm thick, "depressed around stem, bluntly adnate or somewhat decurrent (finally)", pale dingy ocher-yellow, (Smith for S. borealis)

Stem:
3-7 x 1-2.5cm, nearly equal, solid; white when young, becoming yellow near top, "base staining vinaceous, then brownish when bruised"; dry, with glandular dots inconspicuous when young, becoming visible on the upper part when mature; "partial veil membranous, white, staining vinaceous gray, not leaving an annulus", (Bessette), 3-6(8)cm x 1-2.5(3)cm, solid; white and unpolished, becoming yellowish at top and small glandular dots then showing, base where handled staining vinaceous then brownish like the cap; veil "thin, membranous, white, staining vinaceous gray", breaking away from the stem and collapsing on cap margin, when old all traces having disappeared, (Smith), 2-4cm x 1.2-2cm, nearly equal, solid; whitish when young, becoming yellow near top, developing ochraceous tawny to reddish brown tinges, especially near base, when old or when bruised; dry, with glandular dots inconspicuous when young, becoming visible when mature; partial veil purple-brown to reddish brown, covering the pore surface when young, not forming an annulus, (Bessette for S. borealis), 1-5(10)cm x 1-3cm, equal, solid; white becoming yellowish, the base often dingy ochraceous from handling; pinkish brown glandular dots becoming visible by maturity, (Smith for S. borealis)

Chemical Reactions:
flesh stains pink with application of KOH (Bessette), flesh stains vinaceous with application of KOH and grayish with FeSO4, (Bessette for S. borealis)

Odor:
not distinctive (Bessette), slight (Smith for S. borealis)

Taste:
not distinctive (Bessette), mild (Smith for S. borealis)

Microscopic:
spores 6.5-9 x 2.5-3.5 microns, oblong, smooth, colorless to pale honey yellow, (Bessette), spores 6.6-8.8 x 2.8-3.2 microns, oblong, smooth, pale yellow-brown in Melzer''s reagent, colorless to dingy yellow brown in KOH, thin-walled; basidia 4-spored, 18-25 x 4.4-6.6 microns, clavate, colorless to yellowish in KOH and often with amorphous granules, in Melzer''s reagent pale yellowish to brownish; pleurocystidia 40-70 x 8-12 microns, "in fascicles with the bundles surrounded by incrusting pigment more or less bister in KOH", subcylindric to fusoid-ventricose, content colorless to dingy yellow-brown, smooth or with some incrusting debris, thin-walled, cheilocystidia similar but more with brown content and adhering debris, so numerous at times as not to appear clustered; epicutis of cap a gelatinous trichodermium of hyphae 4-9 microns wide and containing numerous dark brown granules in KOH, the walls soon almost completely gelatinized; caulocystidia similar to cheilocystidia; clamp connections none, (Smith), spores 6-9 x 3-5 microns, subcylindric [nearly cylindric] to subelliptic [somewhat elliptic], smooth, colorless, (Bessette for S. borealis), spores 7-8 x 2.8-3 microns, narrowly oblong, smooth, colorless to yellowish in KOH, only slightly more yellowish brown in Melzer''s reagent; basidia 4-spored, many with amorphous red content in KOH; pleurocystidia scattered, 38-50 x 8-12 microns, subfusoid, clavate or cylindric, content and area surrounding the cluster vinaceous-red in KOH and some clusters vinaceous-gray in a few specimens; cap epicutis of hyphae 4-9 microns wide, "appressed on cap surface (probably a collapsed trichodermium), gelatinous and as revived in KOH with numerous minute granules in the gelatinous matrix and along the hyphae (some of these vinaceous in KOH but most are merely yellowish)", in Melzer''s reagent the granules yellowish; caulocystidia "in clusters or scattered and similar to pleurocystidia"; clamp connections none, (Smith for S. borealis)

Spore Deposit:
brown (Bessette), brown (Bessette for S. borealis), pale "orange-cinnamon" when fresh, "cinnamon-buff" after moisture escapes (Ridgway colors), (Smith for S. borealis)