Russula pulverulenta

[ Basidiomycetes > Russulales > Russulaceae > Russula . . . ]

by Michael Kuo

You might easily pass this mushroom by, thinking that it is just another boring, brownish to straw-colored russula. Close inspection, however, reveals Russula pulverulenta to be fairly distinctive--though some might still argue it's boring. What distinguishes this mushroom from many similar russulas is a layer of dense yellowish granules on the young caps; as the mushroom matures and the cap expands, the yellow material breaks up to form soft, yellowish scales, which are scattered across the cap surface.

The scales are easily rubbed off. In other words, they are truly scales--as opposed to the "scales" on Russula virescens or Russula crustosa, which are created by the cap's growth and the cracking up of the surface.

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What, exactly, the powdery granules and scales of Russula pulverulenta are, or what "function" they are serving, is not completely clear. Typically, such things occur on mushroom caps either because the cap grows too fast to maintain the surface it had as a button (as in the two Russula species above, or as in Lepiota americana, for example)--or because the warts or patches result from the break-up of a partial veil that covers the young mushroom's gills, protecting them (as in Amanita muscaria).

In Russula pulverulenta, the break-up of the layer of granules into soft warts is obviously caused by the expansion of the cap . . . but what was the layer of granules doing there in the first place? Singer (1962) believed that this mushroom and the similar Russula granulata (see comments below) actually had partial veils, making them extremely rare among russulas. Shaffer (1972), however, analyzed the cell structure of the granules and scales and found them to be closely aligned with the cells of the cap surface, perhaps refuting the partial veil explanation.

If you're thinking, "And I care because . . . ?" I don't blame you. I thought it was kind of interesting, but then again, I'm a mushroom geek. And when I add that I have no information on the mushroom's edibility, and therefore can't recommend it for the table, you are welcome to throw your Russula pulverulenta at my head to see if any "interesting" break-up of floccose scales occurs there, too.

Description:

Ecology: Mycorrhizal with hardwoods or conifers; sometimes found in urban settings; growing scattered to gregariously; summer; east of the Rocky Mountains.

Cap: 3.5-8 cm; convex with an inrolled margin when young, becoming broadly convex to flat with a shallow depression, with a more or less straight margin that is prominently lined or grooved; dry or slightly moist; when young covered by a dense layer of orange-yellow to yellow granules, eventually breaking up to form loose scales of yellowish to yellow-brown material (in maturity the scales are sometimes inconspicuous); the "base color" underneath the scales dark grayish brown to yellowish brown; skin peeling away easily at the margin, sometimes more than half-way to the center.

Gills: Attached to the stem; close or almost distant; not generally forking, or occasionally forking near the stem; white; sometimes discoloring brownish to yellowish in age.

Stem: 3.5-5 cm long; 1-2 cm thick; white overlaid with yellow granules, eventually whitish towards the top and yellowish below; sometimes discoloring yellowish brown with age; dry; often becoming cavernous (see illustration); smooth.

Flesh: White to yellowish white, unchanging; olive to olive brown around worm holes.

Taste: Gills mild or "fleetingly acrid"; other parts same; odor not distinctive or slightly fragrant to foul.

Spore Print: Pale orange yellow (cream colored).

Microscopic Features: Spores 6-8 x 5-7 µ; with warts .4-1.2 µ high; broadly elliptical or nearly round.

REFERENCES: Peck, 1902. (Kauffman, 1918; Shaffer, 1972; Arora, 1986). Herb. Kuo 09010203.

Russula granulata is a very similar species, difficult to distinguish on the basis of macrocharacters or microcharacters. The principal visual difference is in the color of the granules/scales, which are "reddish brown, brown, yellowish brown, or light yellowish pink to pale orange yellow" (Shaffer, 1012). Don't you just love mycologists' color descriptions? Under the microscope, evidently, the granules/scales of Russula granulata have smooth, colorless cells, while the equivalent cells for Russula pulverulenta are yellowish and warted; most other microfeatures are nearly identical.

Cite this page as:

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