Lactarius fumosus

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by Michael Kuo

Lactarius fumosus is a common summer milky cap in eastern North America, recognized by its smoky brown cap and the fact that its gills and flesh stain pink to reddish when damaged. It is very variable in its taste, ranging from acrid to mild--a demonstration that taste in Lactarius is not always what it is made out to be, identification-wise.

Similar species include Lactarius subvernalis var. cokeri, which is usually white but sometimes becomes somewhat brownish (in which case microscopic analysis will separate the species; see the discussion below), and Lactarius subplinthogalus, which has distant gills, buff to yellowish brown colors, and a frequently scalloped cap margin.

None of these mushrooms should be eaten; edibility is not known.

Description:

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

Cap: 3-10 cm; at first broadly convex, becoming flat or shallowly depressed; dry; fairly smooth; dull smoky brown or paler (occasionally nearly whitish).

Gills: Attached to the stem or beginning to run down it; close or crowded; pale; staining pink to reddish when sliced.

Stem: 4-11 cm long; up to 1.5 cm thick; more or less equal; smooth, without pot-holes; colored like the cap or paler; often whitish near the base; bruising slowly pinkish to reddish.

Flesh: Whitish; staining pink to reddish on exposure.

Milk: White; not changing but staining tissues pink to reddish.

Odor and Taste: Odor not distinctive; taste variable, ranging from acrid or peppery to mild.

Spore Print: Pale cream to buff.

Chemical Reactions: KOH on cap negative.

Microscopic Features: Spores 6-8 µ; round or nearly so; ornamented with spines .5-1.5 µ high; with connecting ridges forming incomplete to complete reticula. Prominently projecting pleurocystidia and cheilocystidia absent.

REFERENCES: Peck, 1872. (Saccardo, 1887 [fuliginosus var. fumosus]; Hesler & Smith, 1979; Smith, Smith & Weber, 1979; Phillips, 1991/2005; McNeil, 2006.) Herb. Kuo 06199604, 07240401, 09300406, 07200707.

Hesler & Smith (1979) describe Lactarius fumosus var. fumosoides, with gills that run down the stem and a pileipellis that contains more inflated elements.

Separating Lactarius fumosus from Lactarius subvernalis var. cokeri can frequently be accomplished by comparing colors; the latter species is usually more or less white, while the former is usually brown. However, brownish versions of Lactarius subvernalis var. cokeri and whitish versions of Lactarius fumosus are not uncommon. Microscopic analysis will separate the two species more definitively (in my collections, at least). While sporal details are cited by some authors as reliable separators, the spores in my collections have demonstrated fairly substantial variability in the height of ornamentation and the "completeness" of the reticulation. Instead, I have found the presence or absence of prominently projecting cystidia--on the faces or edges of the gills--to be a more reliable separator; Lactarius fumosus has none, while Lactarius subvernalis var. cokeri has cystidia that project prominently.

Further Online Information:

Lactarius fumosus in Hesler & Smith (1979)
Lactarius fumosus at Roger's Mushrooms

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Cite this page as:

Kuo, M. (2007, September). Lactarius fumosus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/lactarius_fumosus.html