phragmidium

from The Century Dictionary.

• noun A genus of rust-fungi, of the order Uredinales, having æcidia of the Cæoma type, uredospores with numerous germ-pores, and several-celled teleutospores. About 30 species are known, some of which cause serious diseases of cultivated plants. P. subcorticium attacks the leaves and stems of roses. See rose-rust.