The term "bracket" has been given to those hard, woody fungi that grow on trees or timber in the form of semicircular brackets. They belong to the order Polyporeae, distinguished by the layer of tubes or pores on. the under surface within which the spores are borne. The mycelium, or vegetable part of the fungus, burrows in the tissues of the tree, and often destroys it; the "bracket" represents. the fruiting stage, and produces innumerable spores which gain entrance to other trees by some wound or cut surface; hence the need of careful forestry. Many of these woody fungi persist for several years, and a new layer of pores is superposed on the previous season's growth.