Russula nigricans

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by Michael Kuo

Russula nigricans belongs to a cluster of several species, all of which have whitish to brownish caps and flesh that turns pinkish to red on exposure to air--then, over time, darkens to grayish or black. Russula nigricans is the easiest species in the cluster to recognize; unlike the others, it has distant gills and is often (though not always) somewhat slimy, at least when young and fresh. The similar Russula densifolia has close or crowded gills, and larger spores. See the comments below, as well as the Key to Blushing Russulas, for help distinguishing other species in the cluster.

Reports vary on the edibility of the species in the Russula nigricans cluster. At best, however, they are edible for some and inedible or even poisonous for others, causing gastric upset. Reports from those who have eaten the mushrooms in question are not stellar, anyway. All in all, the "blackening russulas" are not good candidates for culinary experiments.

Description:

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

Cap: 5-15 (sometimes up to 20) cm; broadly convex when young, later flat with a central depression, or shallowly vase-shaped; slimy at first or when wet; more or less smooth; initially whitish but soon discoloring to brownish, ashy gray, or blackish; the margin not lined; without an easily discernible/separable "skin."

Gills: Attached or running very slightly down the stem; thick; distant, or nearly so; white to cream, eventually grayish, bruising blackish, usually with a reddish phase first.

Stem: 3-8 cm long; 1-4 cm thick; whitish at first, soon darkening like the cap; bruising reddish, then blackish over the course of as much as half an hour; smooth.

Flesh: White; hard; bruising promptly or slowly reddish on exposure, then blackish over the course of as much as half an hour or more.

Taste: Inconsistently recorded; mild or slowly slightly to very acrid. Odor inconsistently recorded; slightly fragrant, somewhat unpleasant, or not distinctive.

Spore Print: White.

Microscopic Features: Spores 6-8 x 5-7 µ; with ornamentation under .5 µ high, connected by amyloid ridges forming a partial or complete reticulum; widely elliptical to nearly round.

REFERENCES: Fries, 1838. (Kauffman, 1918; Shaffer, 1962; Arora, 1986; Phillips, 1991/2005.) Herb. Kuo 07259404, 09040202, 02200303, 08030403.

Russula densifolia has close or crowded gills, and spores 7.5-10 x 6-8 µ. Several other "species" have been separated by Robert Shaffer (1962) on the basis of obscure microscopic details--for example, Russula dissimulans, which differs from Russula densifolia in virtually no feature, under the microscope or otherwise, except in the thickness of the cap skin. I have done my best to key these and other "blushing" species out in the Key to Blushing Russulas.

Further Online Information:

Russula nigricans at Macrofungi of Costa Rica
Russula nigricans at Roger's Mushrooms
Russula nigricans at Fungi of Poland

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Cite this page as:

Kuo, M. (2005, January). Russula nigricans. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/russula_nigricans.html