Rust fungus in a leaf. Light micrograph of a section through a wheat leaf infected with the parasitic Puccinia graminis rust. Two uredia, containing stalked unicellular urediniospores (spores, red), can be seen bursting through the epidermis (blue). The base of the uredinium contains hyphae (tubes), which pierce the cells and suck out nutrients. Magnification: x70 when printed 10 centimetres wide.
