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The Genus Pluteus  

[ Basidiomycota > Agaricales > Pluteaceae . . . ]

by Michael Kuo

The mushrooms in Pluteus are wood-decomposing saprobes with gills that are free from the stem and pink spore prints (though what mycologists call "pink" is not always what might come to your mind or mine; "brownish pink" or even "pinkish brown" might be more accurate). There is no volva at the base of the stem, which separates them from volvarielloid mushrooms. The spores, under a microscope, are smooth and round or ellipsoid—separating them from the spores of entolomatoid mushrooms, which are angular and/or ridged. Entolomas do not typically grow on wood, however, so a microscope shouldn't be necessary to identify a Pluteus to genus.

Identifying a Pluteus to species, however, ranges from fairly easy to very difficult, and microscopic analysis is often needed. Important macroscopic features include the color and texture of the cap and stem surfaces, sizes and proportions, and an assessment of whether the specimen was growing on the wood of conifers or hardwoods. Under the microscope, a Roman aqueduct section, mounted in 2% KOH, should be used to observe the pileipellis, pleurocystidia, cheilocystidia, and spores. These microfeatures are used extensively in Pluteus identification, and the genus is fairly easily broken up into groups of species based on them. The pileipellis can be "cellular" (containing inflated, round-ish elements) or it can be a cutis (containing long, cylindric elements)—or, in a few cases, it can contains both types of elements. The cystidia are variously shaped, and can feature thick or thin walls, as well as apical "prongs" that are reminiscent of antlers or horns. And, in a few cases, measuring spores and assessing their shapes (globose to subglobose to ellipsoid) is necessary for identification.

Researchers have made big strides, recently, in assessing the Pluteus species in many parts of the world, including North America. Papers by Alfredo Justo and collaborators (2011a, 2011b, 2011c, 2014) and by Andrew Minnis and collaborators (2006, 2010) have made important contributions. But we are only beginning to get a contemporary picture of what our continent's species are, and large gaps remain. In some cases, previously named species have turned out to represent the same thing, simplifying the picture . . . but in other cases (notably the Pluteus cervinus group), "cryptic" species have been uncovered, some of which are apparently virtually impossible to separate without DNA analysis.

The key below treats 40 North American species of Pluteus, and it is based in large part on the more recent treatments mentioned above. For the most part, I have eliminated poorly documented species that were named over a hundred years ago (usually by William A. Murrill) and never collected again—but I have included some of the contemporary species that have not been collected much, in order to provide modern names and concepts and to encourage further documentation of these species. The result, however, may be frustrating to those who don't want to learn mushroom microscopy, and/or who want "Pluteus cervinus" to be the easily applied name that it used to be.


Pluteus cervinus

Pluteus leoninus

Pluteus granularis

Pluteus cervinus

Pluteus romellii

Key to 41 Species of Pluteus in North America  

1.With a partial veil that forms a ring on the stem; cap yellow.

1.Partial veil and ring absent; cap variously colored.

2.Stem bruising and discoloring bluish to greenish.

2.Stem not bluing.

3.Found east of the Rocky Mountains; odor usually strong and unpleasant; pileipellis a cutis; pleurocystidia thick-walled.
Pluteus americanus
(= "P. salicinus")

3.Variously distributed; odor not distinctive; pileipellis cellular; pleurocystidia thin-walled.

4.Pleurocystidia colorless; broadly lageniform to utriform; known from California to Michigan.
Pluteus cyanopus

4.Pleurocystidia brown in KOH; narrowly lageniform; known from the San Francisco Bay area.
Pluteus phaeocyanopus

5.Cap bright red to orange.

5.Cap otherwise colored.

6.Cap 2–5 cm across, bright red, fading to orange; widely distributed in North America (but more common east of the Rockies).

6.Cap 1–1.5 cm across, scarlet when young but eventually "almost striped yellow on more orange ground" (Singer, 1956); recorded from Florida, Cuba, and Trinidad.
Pluteus laetifrons

7.Gill edges dark (brown to gray or blackish) at maturity, contrasting with the faces.

7.Gill edges not as above.

8.Mature cap 1–2 cm across; pileipellis cellular; usually on the wood of hardwoods.
Pluteus eludens
(= "P. eugraptus")

8.Mature cap more than 2 cm across; pileipellis a cutis; on wood of conifers.

9.Cap and stem finely mealy-granular or velvety; center of cap usually becoming veined.
Pluteus umbrosus

9.Cap and stem not granular or velvety; cap center not usually becoming veined.

10.Gill edges brown only from about the halfway point to the margin; prongs on pleurocystidia often branched; known from northern or northern-temperate transition regions.
Pluteus eos

10.Gill edges brown for entire length; prongs on pleurocystidia not branched; variously distributed.

11.Widely distributed in North America; most spores 7 µm long or longer; pleurocystidia with 2–5 prongs.

11.Known from the southern Appalachians; most spores under 7 µm long; most pleurocystidia with 2 prongs.
Pluteus atrofibrillosus

12.Mature cap yellow to brownish yellow.

12.Mature cap not yellow.

13.Stem long and slender (4–10 cm x 3–6 mm); cap 3–5 cm across, often brownish to brownish yellow when young but soon brownish yellow to yellow overall, the surface finely granular; pileipellis a cutis.

13.Stem not long and slender; cap smaller than above, bright yellow, and bald; pileipellis cellular.

14.Cap white or whitish overall—or with a few brown fibers or scales over a white ground color.

14.Cap not white.

15.Distributed from about the 45th parallel northwards; found on wood of birches and alders; mature cap not usually more than 6 cm across.

15.Variously distributed; found on wood of various trees; cap size varying.

16.Cap 4–15 cm across; often appearing in urban areas where trees have been removed, or in woodchips (but also appearing in woods); pleurocystidia thick-walled, with apical prongs.

16.Cap under 5 cm across—or, if larger, then also finely granular-tomentose; usually appearing in woods; pleurocystidia thin-walled, lacking prongs.

17.Cap and stem finely granular-tomentose; cap 3–6 cm across at maturity; appearing on the deadwood of conifers (rarely the wood of hardwoods) in northern and montane North America.

17.Cap and stem not granular-tomentose; cap smaller than above; substrate and range varying.

18.Cap margin not lined; pileipellis a cutis.
Pluteus niveus

18.Cap margin lined at maturity; pileipellis cellular.

19.Pleurocystidia with long necks.
Pluteus pallidus

19.Pleurocystidia without long necks.
Pluteus roseocandidus

20.Stem yellow; pileipellis cellular.

20.Stem not yellow; pileipellis varying.

21.Fresh cap and stem densely covered with brown granules; cap usually 3–6 cm across; pleurocystidia thin-walled; pileipellis a cutis.

21.Cap and stem not densely covered with brown granules; cap size varying; pleurocystidia varying; pileipellis varying.

22.Cap medium sized to large (regularly 4–5 cm wide or more at maturity); mushroom belonging in "Section Machopluteus."

22.Cap smaller than above; mushroom belonging in "Section Wimpopluteus."

23.Growing on woodchips, or on stumps of recently cut hardwood trees in urban areas; fusiform intermediate cystidia (illustration) usually abundant.

23.Growing in woods; fusiform intermediate cystidia present or absent.

24.Usually found on wood of conifers.

24.Usually found on wood of hardwoods.

25.Found in western North America.

25.Found east of the Rocky Mountains.

26.Clamp connections absent from pileipellis.
Pluteus exilis

26.Clamp connections present in pileipellis.

27.Cap usually pale gray, rarely brown; montane (known from the Cascades and the Sierra Nevada); pleurocystidia with inconspicuous prongs.
Pluteus orestes

27.Cap usually brown; not montane (known from coastal California); pleurocystidia with well-developed prongs.
Pluteus primus

28.Cheilocystidia long (55–120+ µm) and usually cylindric to slightly swollen.
Pluteus primus

28.Cheilocystidia 30–70 µm, club-shaped to sphere-shaped.

29.Spores measuring up to 7.5 µm long and 5 µm wide.
Pluteus hibbettii

29.Spores measuring up to 9 µm long and 6 µm wide.
Pluteus methvenii

30.Clamp connections present in pileipellis.
Pluteus brunneidiscus

30.Clamp connections absent in pileipellis.

31.Fusiform intermediate cystidia (illustration) usually abundant.

31.Intermediate cystidia variously shaped but not predominantly fusiform.

32.Widely distributed; found in urban settings, including woodchips, and in woods; spores 3.5–5.5 µm wide.

32.Probably limited to boreal and northern transitional forests; spores 4.5–6.5 µm wide.
Pluteus rangifer

33.Known from the West Coast, in coastal forests from Santa Cruz County, CA to British Columbia; cap usually dark brown; stem usually scaly.
Pluteus exilis

33.Known from eastern North America; cap brown to dark brown; stem scaly or not.

34.Prongs on pleurocystidia not generally branched or bifurcated.

34.Prongs on pleurocystidia mostly branched or bifurcated.

35.Stem featuring conspicuous brown fibrils; northern and montane species.
Pluteus elaphinus

35.Stem lacking conspicuous brown fibrils; temperate species.
Pluteus hongoi

36.Pileipellis cellular, or cellular with filamentous to cystidioid elements mixed in.

36.Pileipellis a cutis with no cellular elements.

37.Pileipellis composed of both filamentous to cystidioid elements and cellular elements.

37.Pileipellis composed of only cellular elements.

38.Cap often (but not always) developing ridges in a reticulate pattern; cystidia (especially cheilocystidia) with short to long, fingerlike apical projections.

38.Cap not usually becoming ridged and reticulate; cystidia without apical projections.
Pluteus seticeps

39.Tropical to subtropical species; spores mostly globose to subglobose; hymenial cystidia mostly subutriform.
Pluteus jamaicensis

39.Temperate species; spores mostly broadly ellipsoid to subglobose; hymenial cystidia varying.

40.Cap soon notably "rimose" (cracked radially); pileipellis elements variable in size, with frequent large elements (exceeding 40 x 60 µm); pleurocystidia utriform to widely cylindric.

40.Cap not normally rimose; pileipellis elements smaller; pleurocystidia narrowly lageniform, with long necks.
Pluteus phlebophorus

41.Usually found on the wood of conifers.

41.Usually found on the wood of hardwoods.

42.Pleurocystidia with walls under 2 µm thick, without prongs, or with inconspicuous prongs.

42.Pleurocystidia with conspicuous prongs and walls 2 µm thick or more.

43.Spores 7.5–9 µm long; cheilocystidia cylindric, narrowly clavate, or narrowly lageniform.
Pluteus oreibatus

43.Spores 6–7.5 µm long; cheilocystidia widely lageniform to subutriform.
Pluteus fuliginosus

44.Spores averaging 7–7.5 x 4.5–7 µm.
Pluteus hibbettii

44.Spores averaging 7–9 x 5–6 µm.
Pluteus methvenii

45.Pleurocystidia with thin walls, lacking prongs; cap becoming conspicuously grooved from the margin nearly to the center.

45.Pleurocystidia with thick walls and prongs; cap not usually conspicuously grooved.

46.Clamp connections present in pileipellis.

46.Clamp connections absent from pileipellis.

47.Pleurocystidia with walls under 2 µm thick, lacking prongs, or with inconspicuous prongs; known (so far) from Illinois.
Pluteus saupei

47.Pleurocystidia with walls often greater than 2 µm thick, with conspicuous prongs; widespread in North America.
Pluteus brunneidiscus

48.Stem with conspicuous brown fibrils or small scales; boreal and boreal-temperate transitional species.
Pluteus elaphinus

48.Stem lacking brown fibrils; tropical and subtropical species.
Pluteus harrisii


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Cite this page as:

Kuo, M. (2015, July). The genus Pluteus. Retrieved from the MushroomExpert.Com Web site:

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