A genus of uredineous fungi having 4 spore forms (spermagonia, æcidia, uredo- and teleutospores), all produced on the same host. The æcidia are without peridia and paraphyses, and the teleutospores form a dark crust on the surface of the host. The species are numerous and common, causing rusts of various plants. M. farinosa is usually abundant on the leaves of various willows.
rusts having sessile one-celled teliospores in one single level