ABSTRACTNicotine, at concentrations of 1000–3000μl/L in distilled water, induced vacuole formation in teliospores ofUromyces vignae, the causal agent of cowpea rust,Puccinia punctiformis, the causal agent of Canada thistle rust, andPuccinia helianthi, the causal agent of sunflower rust. Induced vacuoles accumulated the vital stain, neutral red, when buffered at high pH values. Vacuole induction by nicotine indicates that the cell walls of these teliospores are permeable and that the inability to germinate is not caused by complete cell wall impermeability.