Thelephora
(from thele, a nipple, and phero, to bear; in allusion to nipple-like growths on the surface of the hymenium in some of the species). A genus of Fungi, most of which grow on the ground in woods. A few, however, are found on tree-trunks or stumps, and at times do mischief to the wood, burrowing between and through the annual rings of growth. Thelephora belongs to the group of Mushrooms in regard to the structure of the hymenium, or part on which the spores are formed, and in four spores being formed from each large cell of the hymenium (see Mushrooms); but it differs from the true Mushrooms in having the hymenium smooth, or bearing mere ridges or warty growths, instead of being spread over gills; and the texture is firm and dry--indeed, almost leathery.
The reproductive organs of T. laciniata appear on the diseased trunks in the form of horizontal, semicircular plates, attached by the middle to the bark or wood; a number of such plates uniting, and overlapping one another, to form a mass 4in. or more across. They are covered above with a coat of fibrous or scaly hairs, prolonged round the margins; and each bears the downy, warty hymenium on its lower surface. The whole mass is dull rusty-brown. This Fungus is usually found among the leaves and other plant-remains in the soil in woods; but it often grows closely around the stems or branches of young trees, and thereby kills small or weakly plants, although it is not a true parasite. It is unsafe to form nurseries for seedlings where T. laciniata abounds, though this species is seldom dangerous to older trees. Dr. Hartig, the well-known German writer on the diseases of trees, has described (in the "Lehrbuch der Baumkrankheiten") a disease of Oak-trunks, widely met with in Germany, which he attributes to a Fungus, named by him T. Perdix. The specific name is the Latin word for a partridge, and alludes to the fact that the wood in which it grows often resembles in its mottlings the plumage of a partridge. The diseased wood turns to a deep red-brown, with numerous white spots of mycelium. These spots soon become closed cavities, which are lined with the pale threads of the Fungus. The wood rots, turning dark brown, and the cell walls and cell contents decay. The reproductive organs, which are the most readily recognised parts of the Fungus, are semicircular plates from 1/20in. to 1/2in. across, and of a brown-yellow colour; and they grow on the surface of dead branches, or in hollow spaces in the trunks. These plates continue to increase in size year after year. Though so frequent in Germany, T. Perdix does not appear to have been recorded as British.
Another Fungus formerly known as T. hirsuta, but now named Stereum hirsutum, is very frequent in Britain, on stumps and dead wood of many species of trees. It also is regarded by Dr. Hartig as at times very hurtful to Oak-wood. In general appearance it is much like a true Thelephora, but differs in having between the hymenium and its support (pileus) a fibrous layer that is not present in Thelephora. The reproductive bodies of Stereum hirsutum are somewhat like those of T. laciniata in general form; but they are usually pale, and are covered above with grey or pale down, and the hymenium is yellowish. Where this Fungus gains an entrance into an Oak-trunk, the wood becomes brown, at first on one side, then gradually all round, in concentric layers. In the brown wood there next appear snow-white or yellowish, longitudinal streaks, which, in cross-sections of the trunk, show themselves in the form of small spots. Where air gains free access, through cracks, &c., the wood may become uniformly yellowish, the middle layer of the wall between the cells is dissolved out, and the tenacity of the wood is destroyed by the cells thus becoming separated. Fortunately, Stereum hirsutum does not often attack healthy trees. As is the case with almost all internal parasites, comparatively little can be done to cure the evil in a tree; though timely removal of diseased branches may prevent the mycelium from reaching the trunk. But, except in the case of choice specimens, the wise course is to remove and burn, without delay, such trees as show signs of being occupied by the Fungi, in order to prevent the latter from spreading to healthy plants.