Rust fungus spores. Scanning Electron Micrograph of two spore types produced by the rose rust fungus Phragmidium sp., emerging from the leaf of a rose plant. Rust fungi (Uredinales) are common parasites on both wild and cultivated plants, often causing severe disease. They have extremely complex life cycles which may involve up to two hosts and five distinct types of spore. Two types of spore representing the fungi's reproductive cycle are seen here. Teliospores are large, stalked objects (at upper left); uredospores are smaller rods (at lower right). Magnification: x950 at 10x7 inch size.