Comments are made on recent publications that emphasize that dioecy in seed plants can be more than just an outcrossing mechanism. It is accepted that "sexual selection" may play an important role in the evolution of dioecy. Circumstantial evidence is presented that when habitat conditions favor outcrossing easily evolved dioecy may be selected. Nevertheless, the disputed suggestion made by me a quarter of a century ago that dioecy appears to have arisen more frequently in hermaphrodite or monoecious taxa that do not have the genetical resources to produce a functional self-incompatibility system is defended, with some indication that this relationship should be examined at the genus level rather than at the level of the family as originally proposed. Disadvantages (to the plants) of dioecy compared to a self-incompatibility system, particularly a monomorphic multiple-allele one, are considered in this light. Distyly is the only incompatibility breeding system that may be expected to give rise sometimes t...