In the following pages I propose to give a review of the teratological cases which botanists, cultivators and amateurs have sent to me for examination or have been collected by myself. As the title indicates both deviations and variations will come into discussion because slight deviations occur so frequently as to be considered as inherent to the species and only modify the character of the plant by way of a stronger development. This is e.g. the case with the genus Cyclamen, where peduncle and the leaf at its base often just cohere but also may coalesce along their whole length, even to such a degree that the petiole reaches beyond the peduncle, which means a striking deviation. The same thing applies to other oscillations moving between extremes and thus rendering the limitation between variations and deviations difficult e.g. the shape of the corolla-lobes, that of the calyx, the hairiness etc. A very striking deviation is shown by the tree-cyclamen, which develops, instead of isolated flowers, one stem with leaves and flowers and somewhat imitates a rhizome. In this case the question arises i whether we have to do with a monstrosity or with a variation which for aught I know has as yet been met with only in C. persicum *). The cases which I want to deal with in the following pages about various families are meant as a modest supplement of the admirable work of O. Penzig at Genoa.