puccinia

Century Dictionary and Cyclopedia

1. n. A genus of parasitic fungi of the class Uredineæ; the rusts. Plants of this genus exhibit the phenomenon of heterœcism—that is, they pass through different stages of their life-history upon different host-plants. P. graminis, one of the commonest and most destructive species, may be taken as a type. It appears in the spring on the leaves of Berberis vulgaris. constituting what is known as barberry-rust or barberry cluster-cups. This is the æcidial stage, and received the name of Æcidium Berberidis before the heterœcism was suspected. Later in the season the uredo stage makes its appearance on the leaves and stems of the cultivated oats, wheat, etc., appearing as pale-yellowish or whitish spots on the leaves. Soon the tissues are ruptured, and the long lines of orange-red uredospores are exposed, now constituting the red rust of oats, etc. By the rapid germination of the uredo-spores the disease is quickly spread, and may involve the entire plant. In the fall, just before cold weather, the black teleutospores are produced. This is known as the black rust, and is designed to carry the fungus over the winter, when it again begins its life-cycle on the barberry. About 450 species of Puccinia are known, not a few of which are serious pests to the agriculturist or horticulturist. See heterœcism, barberry-fungus, rust, Uredineæ.
2. n. A plant of this genus.

WordNet 3.0

1. n. type genus of the Pucciniaceae; a large genus of parasitic fungi including many that are destructive to various economic plants