The effect of water solution of a mixture of glycosides from oleander (<i>Nerium oleander</i> L.) on the germination of pollen grains and on the mitosis of the generative nucleus in <i>Tradescantia bracteata</i> Small and <i>Allium cepa</i> L. has been studied. An inhibition of the germination and of the growth of pollen tubes was observed, proportionally to the concentration of glycosides. The pollen grains of <i>A. cepa</i> are more sensitive. The disturbances in mitosis lead to the formation of two or more uneven-sized doughter nuclei, or to the formation of restitution nuclei. These anomalies are more numerous in <i>T. bracteata</i>. From these results d t appears that pollen grains of <i>A. cepa</i> are characterized by a generally high physiological sensitivity and a small mitotic sensitivity, wheras for <i>T. bracteata</i> the opposite is true.