Patterns of reproduction were studied in a series of inter- and intraspecific units in the genus Avena. The range of variation of the mating system is from autogamy to allogamy. The first system is expressed in cultivated types, while the second is observed in wild and weedy ones. In a wild oat of putative hybrid origin or being a mutation, the development of pollen grains deviates from that noted in grasses as normal.