Plate IV. Structure of the Agaricini, Gill-bearing Mushrooms.

AGARICINI. Fries.

Leucospori (spores white or yellowish).

Genus Lactarius Fries. The plants of this genus have neither veil nor volva. They somewhat resemble the Russulæ, but can be readily distinguished from them by the greater fleshiness of the stem and by the milky juice which exudes from the flesh. The latter is a characteristic feature of the Lactars, giving to the group its name.

The species were originally arranged by Fries into groups according to the color and quality of the milk, and of the naked or pruinose character of the gills. Prof. Peck, however, considering the latter character not sufficiently constant or obvious to be satisfactory, in his early reports makes the color of the milk alone the basis of the primary grouping of the American species.

Saccardo, in his Sylloge, follows Fries in his classification of the species of the genus Lactarius.

In some species the milk is at first bright colored and continues unchanged; in others it is always white or whitish, and in others again it is at first white, changing to different hues on exposure to the air, becoming pinkish, pale violet, or yellow. In one species (C. indigo) both plant and milk are of indigo blue. The taste of the milk varies, as does that of the flesh, according to species. Sometimes it is mild or very slightly acrid, and again it resembles Cayenne pepper in its hot, biting acridity. It is somewhat viscid or sticky in character, and permeates to some extent the whole flesh of the mushroom, but is most profuse in the gills, where in fresh young specimens it is seen exuding on the slightest pressure. In old or wilted specimens it does not flow so freely, but may be found by breaking off portions of the cap.