Uredo (Lat. Urere To Burn), a genus of fungi, to which were formerly referred those minute plants which, under the names of smut, bunt, and rust, sometimes produce such disastrous effects upon grain and grasses. The later authorities in this department of botany place the fungi so injurious to grain crops in other genera; those causing what is known as grain mildew are placed in puccinia; that which injures the grain of wheat, and is known as bunt, is a Tilletia; the various smuts are included in wtilago; and the species thus left in uredo are not found upon crop plants to an injurious extent. For a general account of these and their polymorphism see Fungi; an illustration of the effects of one most injurious to our agriculture is given under Maize; for more popular descriptions, see "Rust, Smut, Mildew, and Mould," by M. C. Cooke (London, 1865), and a more recent work by the same author, edited by the Rev. M. J. Berkeley, "Fungi, their Nature and Uses" ("International Scientific Series," New York, 1875).