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..
In Panceolus the pileus is somewhat fleshy, or thin, the margin even, that is, not striate. The margin extends beyond the gills, and the gills are not uniform in color, being clouded or spotted with black and brown colors, the edge of the gills often white in contrast. The spores are black. The stem is usually smooth, sometimes tloccose scaly, often long, firm, generally hollow. The veil is of interwoven threads, sometimes quite compact, especially when the plants are young. Peck, 23rd Report N. Y. State Mus., p. 10 et seq., gives a synopsis of five species.
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.
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 10-12x15-18//. 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 this condition of the veil can be seen, for on drying the veil collapses. Water is sometimes caught under the veil before the pileus separates far from the stem, and the spores falling thus float against the stem at this point and make a dark ring around the stem, which, however, should not be mistaken for the annulus. In no case was the veil observed to cling to the stem, and many plants have been observed to see if this variation might present itself.
Panaeolus retirugis, section of caps showing form and position of gills (natural size).
Panaeolus retirugis, showing rugose character of cap in left-hand plant (natural size). Copyright.
Panaeolus retirugis, showing cracked surface of cap in the left-hand plant, also in same plant the ring mark of black spores which lodged before veil ruptured; in other plants showing well the V-shaped loops of veil on margin of cap (natural size). Copyright.
This peculiarity of the veil in clinging to the margin of the pileus has led Hennings to place the plant in Karsten's genus (Engler and Prantl, Pflanzenfamilien) Chalymotta, as Chalymotta retirugis. The plants have several times been eaten raw by me, and while they have a nutty flavor and odor, the taste is not entirely agreeable in this condition, because of the accompanying slimy sensation.
A number of smaller species, among them P. fimicola Fr., and P. papilionaceus Fr., occur in similar places. Panaeolus solidipes Pk., is a large species with a long, solid stem, growing on dung. Psilocybe fœnisecii, abundant in lawns and grassy places during late spring and summer, resembles a Panaeolus. The cap shows zones of light and dark color, due to different amounts of water, which disappear as the plant matures. It belongs to the purple-brown-spored agarics.