=Lactarius corrugis= Pk. =Edible.=--This species occurs with _Lactarius volemus_ and very closely resembles it, but it is of a darker color, and the pileus is more often marked by prominent wrinkles, from which character the plant has derived its specific name. It is perhaps a little stouter plant than _L. volemus_, and with a thicker cap. The surface of the =pileus= seems to be covered with a very fine velvety tomentum which glistens as the cap is turned in the light. The =gills= are much darker than in _L. volemus_. The plants are usually clearly separated on account of these characters, yet there are occasionally light colored forms of _L. corrugis_ which are difficult to distinguish from dark forms of _L. volemus_, and this fact has aroused the suspicion that _corrugis_ is only a form of _volemus_. The milk is very abundant and in every respect agrees with that of _L. volemus_. I do not know that any one has tested _L. corrugis_ for food. But since it is so closely related to _L. volemus_ I tested it during the summer of 1899 in the North Carolina mountains. I consider it excellent. The methods of cooking there were rather primitive. It was sliced and fried with butter and salt. It should be well cooked, for when not well done the partially raw taste is not pleasant. The plant was very abundant in the woods, and for three weeks an abundance was served twice a day for a table of twelve persons. The only disagreeable feature about it is the sticky character of the milk, which adheres in quantity to the hands and becomes black. This makes the preparation of the plant for the broiler a rather unpleasant task. Figure 118 is from plants (No. 3910, C. U. herbarium) collected in the woods at Blowing Rock, during September, 1899. Just before the exposure was made to get the photograph several of the plants were wounded with a pin to cause the drops of milk to exude, as is well shown in the illustration. The dark color of the lamellæ in _L. corrugis_ is due to the number of brown cystidia or setæ, in the hymenium, which project above the surface of the gills, and they are especially abundant on the edge of the gills. These setæ are long fusoid, 80--120 × 10--12 µ. The variations in the color of the gills, in some plants the gills being much darker than in others, is due to the variations either in the number of these setæ or to the variation in their color. Where the cystidia are fewer in number or are lighter in color the lamellæ are lighter colored. Typical forms of _Lactarius volemus_ have similar setæ, but they are very pale in color and not so abundant over the surface of the gills. In the darker forms of _L. volemus_ the setæ are more abundant and darker in color, approaching those found in _L. corrugis_. These facts, supported by the variation in the color of the pileus in the two species and the variations in the rugosities of the pileus, seem to indicate that the two species are very closely related.