ABSTRACTNeovossia horridateliospores were studied by the use of scanning electron microscopy, transmission electron microscopy, and freeze-fracture replicas. Surfaces of these spores are covered with rodlet-like structures which differ from those reported previously in other smut fungi, such asTilletia indica.The rodlet-like structures are individually distinct and are not grouped into fascicles. They ranged between 14.3 and 22.5 nm in width and averaged 18.1 nm. In length they ranged from about 80 to 110 nm and averaged 97.2 nm. Dormant teliospores have thick spore walls composed of four distinct layers. The partition layer is composed of lamellar wavy surfaces. The periodicity of the pattern on these surfaces ranged from 13.3 to 14.2 nm with an average of about 13.8 nm. The plasma membrane contained invaginations and numerous particles which are characteristic of other grass smut fungi. The cytoplasm also contained inclusion vacuoles and unidentified organelles.