The plants belonging to this family vary greatly in size, form, and consistency. Some of them are very large, some quite small, some are fleshy in consistency, some are woody, corky; some membranaceous; and if we include plants formerly classed here, some are gelatinous, though there is a tendency in recent years on the part of some to place the gelatinous ones among the trembling fungi. The special character which marks the members of this family is the peculiarity of the fruiting surface, just as a number of the other families are distinguished by some peculiarity of the fruiting surface. In the HydnaceÆ it covers the surface of numerous processes in the form of spines, teeth, warts, coarse granules, or folds which are interrupted at short intervals. These spines or teeth always are directed toward the earth when the plant is in the position in which it grew. In this way the members of the family can be distinguished from certain members of the club fungi belonging to the family ClavariaceÆ, for in the latter the branches or free parts of the plant are erect.

In form the HydnaceÆ are shelving, growing on trees; or growing on the ground they often have a central or eccentric stem, and a more or less circular cap; some of them are rounded masses, growing from trees, with very long spines extending downward; others have ascending branches from which the spines depend; and still others form thin sheets which are spread over the surface of logs and sticks, the spines hanging down from the surface, or roughened with granules or warts, or interrupted folds (see Phlebia, Figs. 193, 194). In one genus there is no fruit body, but the spines themselves extend downward from the rotten wood, the genus Mucronella. This is only distinguished, so far as its family position is concerned, from such a species as Clavaria mucida by the fact that the plant grows downward from the wood, while in C. mucida it grows erect.

HYDNUM Linn.

The only species of the HydnaceÆ described here are in the genus Hydnum. In this genus the fruiting surface is on spine, or awl-shaped processes, which are either simple or in some cases the tips are more or less branched. The plants grow on the ground or on wood. The species vary greatly in form. Some are provided with a more or less regular cap and a stem, while others are shelving or bracket shaped, and still others are spread out over the surface of the wood (resupinate).

Hydnum coralloides Scop. Edible.—Among the very beautiful species of the genus Hydnum is the coral one, Hydnum coralloides. It grows in woods forming large, beautiful, pure white tufts on rotten logs, branches, etc. The appearance of one of these tufts is shown in Fig. 195. There is a common stem which arises from the wood, and this branches successively into long, ascending, graceful shoots. The spines are scattered over the entire under side of these branches and hang down for 3–6 mm. They are not clustered at the ends of the branches, as in the bear's head hydnum, and the species can be easily distinguished by giving attention to the form of the branching and the distribution of the spines on the under side of the branches. Figure 195 represents a plant collected at Ithaca, and it is natural size. They grow, however, much larger than this specimen. The species is widely distributed, and not uncommon. It is excellent for food.

Hydnum caput-ursi Fr. Edible.—This plant is also a beautiful one. It is more common than the coral hydnum so far as my observation goes. It is known by the popular name of "bear's head hydnum" in allusion to the groups of spines at the ends of the branches. It occurs in woods with a similar habit of growing on trunks, branches, etc. This plant also arises from the wood with a single stout stem, which then branches successively, the ends of the branches having groups of long pendant spines appearing like numerous heads. Sometimes the spines on the top of the group are twisted or curled in a peculiar way. Large tufts are sometimes formed, varying from 12–20 or more centimeters in diameter. Figure 196 is from a plant collected at Ithaca.

Hydnum erinaceus Bull. Edible.—This plant is sometimes called "Satyr's beard." It grows on dead trunks in the woods or groves, and is often found growing from wounds in living trees. It forms a large, tubercular mass which does not branch. The spines are very long and straight and hang downward in straight parallel lines from the sides of the mass. The spines are from 1–2 cm. or more long. Figure 197 represents one of the plants, showing the long spines.

Hydnum repandum L. Edible.—This plant is not uncommon, and it is widely distributed. It grows usually in woods, on the ground. It varies greatly in size, from very small specimens, 1–2 cm. high to others 10–12 cm. high. The cap is 2–18 cm. broad, and the stem 6–12 mm. in thickness.

It is entirely white or the cap varies to buff, dull yellow reddish or dull brown. It is very brittle, and must be handled with the utmost care if one wishes to preserve the specimen intact. The pileus is more or less irregular, the stem being generally eccentric, so that the pileus is produced more on one side than on the other, sometimes entirely lateral at the end of the stem. The margin is more or less wavy or repand. The spines are white, straight, and very brittle. The stem is even or clavate. Figure 198 is from plants collected at Ithaca during August, 1899, and represents one of the large specimens of the species. In one plant the pileus is entirely lateral on the end of the long clavate stem, and is somewhat reniform, the stem being attached at the sinus. In the other plant the stem is attached near the center. This species is considered one of the best mushrooms for the table.

Hydnum imbricatum L. Edible.—This is a very variable species both in size and in the surface characters of the pileus. It occurs in woods, groves, or in open places under trees. The plants are 3–7 cm. high, and the pileus varies from 5–15 cm. broad, the stem from .5–2.5 cm. in thickness. The pileus is convex and nearly expanded, fleshy, thinner at the margin, regular or very irregular. The color is grayish in the younger and smaller plants to umber or quite dark in the larger and older ones. The surface is cracked and torn into triangular scales, showing the whitish color of the flesh between the scales. The scales are small in the younger plants and larger in the older ones. Figure 200 is from plants collected at Ithaca, and the pileus in these specimens is irregular. The species is edible, but bitter to the taste.

The pileus is first umbilicate or depressed, becoming depressed or infundibuliform, irregular, eccentric, the margin repand, and sometimes lobed, and lobes appearing at times on the upper surface of the cap. The surface is first tomentose or pubescent, becoming smooth, with prominent concentric zones probably marked off by periodical growth; the color is first white, so that the edge is white, becoming cream color to buff, and in age dull brown and sometimes blackish brown in the center of the old plants. The pubescence disappears from the old portions of the cap, so that it is smooth. The pubescence or tomentum is more prominent on the intermediate zones. The margin is rather thick, somewhat acute or blunt, the upper portion of the flesh is spongy and the middle portion tough and coriaceous, and darker in color. The pileus is somewhat pliant when moist or wet, and firm when dry, the dark inner stratum hard.

The spines are first white or cream color, in age changing through salmon color, or directly into grayish or grayish brown. The spines when mature are long, slender, crowded, and decurrent on the upper part of the stem. The spores are white, globose, echinulate, 3–4 µ. The stem is stout and irregular, very closely resembling the stem of Hydnum velutinum, with a thick, spongy, outer layer and a central hard core.

The odor, which resembles that of a perspiring darkey, before the plant is dry, disappears after drying, and then the plant has the same agreeable odor presented by several different species of Hydnum. The odor suggests H. graveolens, but the characters of the stem and surface of the pileus separate it from that species, while the tough and pliant character of the cap separates it from H. fragile. Figure 199 is from plants (No. 4334, C. U. herbarium) collected at Blowing Rock, N. C., during September, 1899.