[Illustration: PLATE 76, FIGURE 194.--Phlebia merismoides. Portion of a plant 2-1/2 times natural size, to show interrupted folds of fruiting surface. For colors see Fig. 193. Copyright.] CHAPTER X. HEDGEHOG FUNGI: HYDNACEAE. 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). [Illustration: FIGURE 195.--Hydnum coralloides. Entirely white (natural size). Copyright.]