This section is from the book "Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc.", by George Francis Atkinson. Also available from Amazon: Studies of American Fungi: Mushrooms, Edible, Poisonous, Etc..
This is known as the sooty lactarius and occurs in woods along with the smoky lactarius. It is distinguished from the latter by the dark brown color of the pileus and by the presence usually of rugose wrinkles over the center of the cap. In size it agrees with the smoky lactarius.
The pileus is convex, then plane, or somewhat depressed in the center, dry, sometimes with a small umbo, dark brown or sooty (chocolate to seal brown as given in Ridgeway's nomenclature of colors), covered with a very fine tomentum which has the appearance of a bloom. The margin of the cap, especially in old plants, is somewhat wavy or plicate as in Lactarius fuliginosus. The gills are moderately crowded when young, becoming distant in older plants, white, then cream color or yellow, changing to reddish or salmon color where bruised. The spores are yellowish in mass, faintly so under the microscope, globose, strongly echinulate, 6-10µ. The taste is mild, or sometimes slowly and slightly acrid. The plants from North Carolina showed distinctly the change to reddish or salmon color when the gills were bruised, and the taste was noted as mild.
Figure 119 is from plants (No. 3864, C. U. herbarium) collected in the Blue Ridge Mountains, at Blowing Rock, N. C, September, 1899.