SUMMARYCollections ofUredo iyoensiswere found to have two kinds of urediniospores (elliptic and mucronate spores). These two kinds of spores are similar in morphology and size to the two kinds of spores reported forU. alpestris.Scanning-electron-microscopic observations showed that the walls of the elliptic spores bear dense warts or ridges in more or less longitudinal lines, and those of the mucronate spores are minutely and sparsely punctate. These two kinds of spores never occur together in the same sorus. This indicates that the two spore forms represent two distinct taxa.Viola blandaeformis, V. selkirkii, V. rossi, andV. kusanoanaare newly added to the host plants forU. iyoensis.