Urediniospores are thin-walled spores produced by the uredium, a stage in the life-cycle of rusts.
Urediniospores of 11 Milesina species. a Milesina blechni on Struthiopteris spicant b Milesina blechni on Struthiopteris spicant, cracked spore with released plasma, germ pores scattered c Milesina carpatica on Dryopteris filix-mas d Milesina exigua on Polystichum braunii, smooth surface e Milesina exigua on Polystichum braunii, smooth surface, plasma-free spore, germ pores bipolar f Milesina feurichii on Asplenium septentrionale with smooth areas on surface g
Germinating urediniospore of Puccinia graminis, model from the late 19th century, Botanical Museum Greifswald