=Panæolus retirugis= Fr.--The color of this plant is not attractive, but it is one of the most beautiful species I have studied, if one regards form and the general features in its development. It is said to occur on dung. I have found it in lawns or grassy places, especially freshly made lawns or greenswards which have been heavily manured. The illustrations in Figs. 45--48 were made from photographs of plants which grew in a newly made boulevard along Buffalo street, Ithaca, N. Y. (No. 2356 C. U. herbarium). The plants are from 7--15 cm. high, the cap from 1--3 cm. in diameter, and the stem is 3--4 mm. in thickness. The size of the plants varies greatly according to the environment, being larger in moist soil and wet weather and smaller in dry soil and dry weather. It occurs in late spring and during the summer. [Illustration: FIGURE 47.--Panæolus retirugis, showing rugose character of cap in left-hand plant (natural size). Copyright.] The =pileus= is oval to ovate and conic, and in some cases it becomes more or less expanded, but never, so far as I have observed, does it become depressed or even plane. In wet weather it is usually at first dark smoky in color, viscid, becoming grayish in age, and as the pileus dries it becomes shining. In lighter colored forms the pileus is at first light leather color to cream color. Toward the center of the pileus are irregular wrinkles or shallow pits, the wrinkles anastomosing more or less, and it is because of this character of the surface of the pileus that the plant receives its specific name. During dry weather there is a tendency for the pileus to crack, separating the dark color of the surface into patches showing the white flesh beneath. The pileus is often umbonate or gibbous, and the center is often darker than the margin. The pileus in rare cases is entirely white. The =gills= are adnate, broad in the middle, and in the more expanded forms as the gills separate more and more from the stem there is a tendency for them to become somewhat triangular. The =spores= are black in mass, are elliptical or short fusiform, and measure from 10--12 × 15--18 µ. The =stem= is cylindrical, sometimes tortuous, smoky gray, light reddish brown, or paler, sometimes entirely white, the lighter forms of the stem accompanying the light forms of the pileus; cartilaginous in texture, becoming hollow, always darker below and paler above, smooth, granulate with minute darker points, bulbous. The =veil= is very prominent and stout when the plant is young, and extends from the margin of the pileus to the stem when the plant is very young and the stem has not elongated. As the stipe elongates the veil separates from the stipe as a ring, and then, as the pileus expands, it is broken quite regularly into short segments which become arranged regularly around the margin of the pileus in the form of the letter V, which gives a beautiful appearance to this stage of the plant. It is only when the plants are fresh and moist that