A SEM investigation of the seeds of 40 European and 5 Asiatic species ofSedum revealed three fundamentally different types of ornamentation of the testa. The most prominent difference in the ontogeny of the seeds differing in ornamentation is the ovular envelope, which is a mucous membrane enclosing the ovules and young seeds and occurring only in plants whose seeds have a simple type of ornamentation. The ornamentation of the testa was found to be a very constant character. Because the ornamentation is highly correlated with the hybridization pattern of the species it is considered to be an important character in the infrageneric classification ofSedum.