Fine Structure of Wheat Stem Rust Uredospores

The fine structure of uredospores and germ tubes of Puccinia graminis f. sp. trilici is described from electron micrographs of cells fixed in KMnO 4 . In terms of their principal cytoplasmic structures (nuclei, mitochondria, endoplasmic reticulum, and protoplasmic and vacuolar membranes) these cells bear a general resemblance to other fungi and higher plants but differences between resting cells and germ tubes were noted in the size of oil bodies and the structure and extent of the endoplasmic reticulum.