Grains of wild oats (Avena fatua L.) may remain dormant in the soil for several years or even for decades. The reasons for this dormancy are not known, but various hypotheses have been advanced to explain it, such as that the hull acts as a barrier to oxygen (1,7), and that a toxic substance is present in the hull as in cultivated oats (5). The tests here reported were undertaken to further explore some aspects of the problem of dormancy in wild oats.