Tylopilus badiceps

[ Basidiomycetes > Boletales > Boletaceae > Tylopilus . . . ]

by Michael Kuo

I am using the label "Tylopilus badiceps" for eastern North American, oak-associated Tylopilus collections that share the following features:

• A cap that is finely velvety and purple-brown ("maroon"), at least when young;
• A pore surface that may or may not bruise brown but is whitish before becoming dingy pinkish tan at maturity;
• A stem that is flushed with the cap color, even when young, before bruising or discoloring;
• A mild (rather than bitter) taste;
• A pileipellis with at least some areas composed of cystidioid elements (see the illustration) that are yellowish in KOH.

If you don't have a microscope, go ahead and skip that last feature; it may not matter. If you have matched all the naked-eye features above except for the purple-brown color and your mushroom is merely "brown" or "reddish brown," I suggest calling it "Tylopilus ferrugineus"--but if you have a brown-capped, similar Tylopilus with a whitish stem (before it discolors when you handle it), see Tylopilus indecisus. My concept of Tylopilus badiceps is certainly debatable (and leaves little or no distance between it and Tylopilus ferrugineus); see the extended commentary below if you care.

Mild-tasting Tylopilus species with brown to purple-brown caps and (initially) pale pore surfaces are all presumed to be edible.

Description:

Ecology: Mycorrhizal with oaks; growing alone, scattered, or gregariously; summer and fall; widely distributed in eastern North America.

Cap: 3-10 cm; convex to broadly convex or nearly flat in age, but often with a distinctively folded or creased edge, described as "truncate or beveled" by the original author of the species (see the illustration to the right), creating a flat-sided profile when viewed from the side; dry; finely velvety when young; purple-brown when young, fading to pinkish brown or tan.

Pore Surface: Whitish when young, becoming dingy pinkish tan with age; often bruising brown; pores angular, 1-3 per mm; tubes to about 1 cm deep.

Stem: 4-8 cm long; up to 3 cm thick; more or less equal; smooth; not reticulate; colored like the cap or a little paler--even when young; bruising brown and discoloring brown with age or after handling.

Flesh: White; unchanging or staining pinkish to brownish in spots on exposure.

Odor and Taste: Odor often sweet and thick; taste mild.

Chemical Reactions: Ammonia negative to pinkish or dark red (darker when the cap is young and has more purple in it); negative on flesh. KOH grayish to blackish on cap; negative on flesh. Iron salts olive on cap; olive or bluish gray on flesh. (Data from my own collections.)

Spore Print: Dark pink.

Microscopic Features: Spores 8-10 x 3.5-4.5 µ, according to the Smith & Thiers study of the type collection (1971, p. 122); smooth; subfusiform to elliptical. Spores of my collections have been slightly larger, averaging about 10-11 x 4 µ. This doesn't bother me, since spore size has not been upheld as a consistent and reliable feature in contemporary bolete research, but my approach leaves precious little to separate Tylopilus badiceps from Tylopilus ferrugineus. Pileipellis "a compact palisade of pileocystidia 30-40 x 7-10 µ, obtusely fusoid-ventricose varying toward utriform or subclavate-mucronate to clavate, the content yellow in KOH but this soon dissolving" (Smith & Thiers)--but see my comments below.

REFERENCES: (Peck, 1900) Smith & Thiers, 1971. (Peck, 1900; Saccardo, 1902; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Phillips, 1991/2005; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 09020103, 08280501, 06300707.

An "Easy" Species?

Charles Peck described Boletus badiceps over 100 years ago, in 1900. The full text of his description can be found in the right-hand column. Peck obviously considered the folded edge of the cap to be an important character, since he not only described it but commented on it profusely ("profusely" for the frequently tight-lipped Peck). I will disucuss the folded cap edge in a moment, but it is important to note first that Peck's name for the species, badiceps, means "bay stemmed," as in "bay brown," which is a reddish brown sometimes also called "chestnut brown." Although his description merely calls the stem "brownish," the fact that he named the species badiceps indicates Peck wanted to stress that the stem was not pale--as it is, for example, in the similar Tylopilus indecisus.

By the time Saccardo (1902) included Peck's species in his Sylloge Fungorum two years later, he was summarizing Peck's comments as follows:

Species margine pilei oblique truncato facile dignoscitur.

. . . which I translate as, more or less, "A species easily distinguished by the obliquely truncated cap margin." Well, maybe . . . but while I have found specimens I would label Tylopilus badiceps displaying the folded edge, I have also found them without it--and I have found other species of Tylopilus demonstrating the feature (here is one example; though I didn't collect the specimens and therefore can't identify them, they're pretty clearly not Tylopilus badiceps). Thus it is probably a wise decision to insert "usually" (Both, 1993) or "typically" (Bessette et al, 2000) as a qualifier for the folded edge, since one might not always find specimens like the ones I have illustrated on this page (or these, illustrated by Roy Halling), displaying the feature proudly.

The next "easy" feature in the taxonomic history of Tylopilus badiceps comes from Smith & Thiers (1971), who placed the species in the genus Tylopilus and wrote that it is "one of the most easily recognized species in the genus." In case you're wondering, "easy" to Smith & Thiers means: "Pileus cuticle a compact palisade of pileocystidia the cystidia [sic] 30-40 X 7-10 µ." The authors studied Peck's type collection, and found the "pileocystidia" to be everywhere on the cap surface, creating a "turf." They did not illustrate what they were talking about, so we are left with the description found above, under "Microscopic Features." Smith & Thiers also did not cite any collections of Tylopilus badiceps, and Smith appears to have collected what he called Tylopilus badiceps only once, in Washtenaw County, Michigan, in 1973 (based on online records at the University of Michigan Herbarium).

I take "pileocystidia" to mean elements on the cap surface that project in various pointy or inflated ways--shapes that are typical of pleurocystidia on the faces of gills or tubes--and, based on my own analysis of Tylopilus specimens, I am inclined to doubt whether the presence of such elements is constant and predictable, even on the cap surface of a single mushroom. The razor-thin section of the type collection that Smith & Thiers studied may have displayed a dense "turf" of "pileocystidia," but a section from another portion of the cap might have displayed only scattered pileocystidia, or even a cystidium-lacking "normal" trichoderm. I also suspect that this microscopic feature is related to the maturity of the specimen, since the subvelutinous cap may become smoother with age, and the cystidioid elements may be responsible for the fuzziness.

As for current, DNA-based research into Tylopilus badiceps, we have preliminary and very cursory DNA results from Binder & Hibbett (2004, online here; scroll down a bit to find the Tylopilus specimens sampled), in which Tylopilus badiceps forms a well supported clade of purple-capped species with Tylopilus plumbeoviolaceus and Tylopilus rubrobrunneus--and the results of den Bakker & Noordeloos (2005), which contradict the Binder & Hibbett results and place Tylopilus badiceps in a well supported clade with Xanthoconium affine. "Well supported," in DNA study parlance, means that the researchers' software programs are sure of themselves and place a high "bootstrap value" on the results--in short, the computer thinks the results are "easy." Neither study, however, is "well supported" in the parlance of common sense, which would dictate relying on DNA data from many specimens, carefully examined and identified by the researchers themselves and preserved in a public herbarium, rather than a single sequence of the letters C, G, T, and A deposited in GenBank (Accession AY612833) and labeled "Tylopilus badiceps" by some folks at Duke, one of whom (Vilgalys, 2003) has even published a paper entitled "Taxonomic misidentification in public DNA databases." (To be fair, the den Bakker & Noordeloos study is supported in the ways I suggest when it comes to the study's central object, Leccinum, while the Binder & Hibbett study has been placed online but not published in a peer-reviewed context and is clearly intended as a preliminary sketch.)

So much for "easy." Fortunately, researchers at the New York Botanical Garden are currently working on Tylopilus, along with several other bolete genera, and perhaps they will make Tylopilus badiceps "easy" once and for all.

Cited above:

Binder, M. & D. S. Hibbett (2004). Toward a global phylogeny of the Boletales. Retrieved from the Clark University Web site: http://www.clarku.edu/faculty/dhibbett/
boletales_stuff/Global_Boletales_2004_28S.gif

den Bakker, H. C. & M. E. Noordeloos (2005). A revision of European species of Leccinum Gray and notes on extralimital species. Persoonia 18: 511-587

Vilgalys, R. (2003). Taxonomic misidentification in public DNA databases. New Phytologist 160: 4-5.

Further Online information:

Tylopilus badiceps in Smith & Thiers, 1971
Tylopilus badiceps at Roger's Mushrooms

Boletus badiceps

   Pileus firm, convex or somewhat centrally depressed when mature, dry, velvety, obliquely truncate on the margin, bay red or dark maroon color, flesh white, unchangeable, taste and odor mild, sweet, suggestive of molasses : tubes plane, adnate, white or whitish, becoming dingy with age, the mouths minute : stem equal or slightly swollen in the middle, radicating, glabrous, solid, brownish.
   Pileus 4-8 cm. broad : stem 4-5 cm. long, 1.5-3 cm. thick.
   Oak woods. West Philadelphia, Pa. August and September.
   The truncate or beveled margin of the pileus is a striking feature in this species. It is about 4 mm. broad and as even as if cut with a knife. Sometimes the surface of the stem ruptures transversely just below the top, the liberated shreds above curling upward against the tubes and those below curving outward and downward. In mature plants brownish spots appear in the flesh of the pileus. "When cooked it is of high flavor and tender as kidney," C. McIlvaine.

C. H. Peck (1900). Bulletin of the Torrey Botanical Club 27: 18.

Typos, Errors, Etc.

The "radiating" stem of Tylopilus badiceps, mentioned in Smith & Thiers (1971) and again in Phillips (1991/2005), represents a typo for Peck's "radicating" stem, above.

Both (1993) incorrectly cites the volume of Peck's publication as volume "28"; it should read "27." Additionally, "reccish brown" should obviously be "reddish brown."

The spore sizes of "6.5-10.5 X 2.5-4 µm" cited by Bessette, Roody & Bessette (2000) either represent a typo or a substantially different assessment from that of other authors, entirely unsupported by cited references or collections.

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Cite this page as:

Kuo, M. (2007, February). Tylopilus badiceps. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/tylopilus_badiceps.html