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Suillus cothurnatus

[ Basidiomycota > Boletales > Suillaceae > Suillus . . . ]

by Michael Kuo

The morphological differences between Suillus cothurnatus and Suillus salmonicolor are few and far between--and, frankly, pretty unreliable. Both species have orangish-brownish, slimy caps and sheathing, glutinous rings that often feature a flaring, white, lower edge when the mushrooms are young. Some authors claim that the white, baggy edge of the ring is more prominent in Suillus salmonicolor, but I have not found this to be the case. There is also a putative micro-morphological difference recorded by some authors, but I believe the "difference" results from a misinterpretation of Singer's original 1945 description of the species (see the discussion below if you care).

Ultimately the two species (if indeed there are two, rather than one—or many) should be separated on the basis of their mycorrhizal partners: Suillus salmonicolor associates with jack pine, Virginia pine, and pitch pine, while Suillus cothurnatus associates with loblolly pine and longleaf pine (possibly also slash pine).


Ecology: Mycorrhizal with loblolly pine and longleaf pine (possibly also slash pine); growing alone, scattered, or gregariously; late summer and fall, or over winter in warmer climates; widely distributed where the host trees occur (from Texas to Florida and New Jersey). The illustrated and described collections are from Illinois and Georgia.

Cap: 2–6 cm; convex at first, becoming broadly convex; slimy when fresh, but often dry and glossy at maturity; bald, or very finely appressed-fibrillose and appearing streaked under the gluten; dull brownish orange to orangish yellow, with brownish streaks, becoming brownish to yellowish with maturity; the margin at first inrolled.

Pore Surface: At first covered with a thick, whitish to orangish partial veil that is baggy and rubbery, with a white roll of tissue on the lower edge; orangish at first, maturing to brownish orange; not bruising; 1–3 angular pores per mm; not boletinoid; tubes to about 1 cm deep.

Stem: 3–6 cm long; 0.5–1 cm thick; tapered to base; tough; covered with glandular dots that are brownish red at first but become brown to black with age; whitish to yellowish or orangish; with a thick, sheathing, gelatinous, whitish to orangish ring that often features a whitish roll of tissue at the bottom and, in age, collapses to form a grayish, bracelet-like band.

Flesh: Yellowish in cap; darker orange in the stem; deep salmon orange in the stem base; not staining on exposure.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia negative to faintly purplish on cap surface; pinkish to purplish on flesh. KOH purple to gray on cap surface; purple to bluish on flesh. Iron salts negative on cap surface; negative to faintly greenish on flesh.

Spore Print: Cinnamon brown.

Microscopic Features: Spores 7–10 x 2–3 µm; fusiform; smooth; yellowish in KOH. Hymenial cystidia fusiform; dark brown in KOH. Caulocystidia fusiform to cylindric or subclavate; dark brown in KOH.

REFERENCES: Singer, 1945. (Smith, Smith & Weber, 1981; Palm & Stewart, 1986; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 07300908, 10170902, 10141301.

Smith & Thiers (1964) recognized Singer's 1945 species, Suillus cothurnatus, on the basis of his original description, without studying any material (in fact, they simply quoted Singer's description in its entirety, including Singer's "Material studied" list, saying merely that their "account is taken from Singer"). Smith & Thiers declare that "[t]he inflated cells on the stipe seem to be a distinctive character," referring to Singer's description, in which the glandular dots consist "not only of the ordinary dermatocystidia of the Suillus-type but also of hyaline structures recalling the scales of Leccinum . . . showing parallel, multi-septate hyphae terminating in a palisade of sterile, large basidium-like bodies (dermatopseudoparaphyses) and cystidia-like bodies (dermatocystidia of the Leccinum-type, i.e. rather small, hyaline, ampullaceous with narrowed bases)." Singer's minimalist illustrations of the structures he described do not help much in sorting out what, exactly, he meant when describing Suillus cothurnatus as possessing Leccinum-like "dermatocystidia," but they do point to the possibility that he was simply describing caulohymenial structures common to most boletes: caulobasidia, septate caulobasidioles, and caulocystidia. Singer also may have simply observed glandular dots that were immature, and therefore contained hyaline elements; mature glandular dots are usually highly pigmented—so much so that they are often messy with pigment globules and hard to analyze. However, when immature they can be stubbier and hyaline, and they are then more easily described; an observer might easily be led to conclude that the elements were different. I believe Singer may have made this error, and that Smith & Thiers repeated it by regurgitating Singer's account without the extended study of herbarium material that should have been accomplished in order to treat the species in a monograph. Smith later repeated the putative micro-morphological difference in a popular field guide (Smith, Smith & Weber, 1981)—and the misinterpretation is again reiterated in Bessette, Roody & Bessette (2003). In my experience the structures described and illustrated by Singer (see my illustrations to the right) are found not only in Suillus cothurnatus, but also in Suillus salmonicolor and in most species of Suillus.

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Suillus cothurnatus

Suillus cothurnatus

Suillus cothurnatus

Suillus cothurnatus

Suillus cothurnatus
Ammonia, KOH, iron salts

Suillus cothurnatus

Suillus cothurnatus

Suillus cothurnatus

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Kuo, M. (2016, January). Suillus cothurnatus. Retrieved from the MushroomExpert.Com Web site: