THE CAUSE OF INCOMPATIBILITY BETWEEN BARLEY AND RYE

Abstract

When common barley is pollinated by common rye fertilization takes place normally but no viable seeds are produced. The immediate cause of the failure is abnormal development of the hybrid endosperm and particularly of the endospermic nuclei, which from an early stage are of immense size and are always few in number. No cells are ever formed in the endosperm. It collapses on the fifth or sixth day after pollination and disintegrates. The hybrid embryo, on the other hand, although it grows more slowly than the pure barley embryo from the third day, remains normal and healthy in appearance long after the endosperm has become very abnormal or has completely collapsed. The behaviour of the maternal tissues of crossed material is similar to that of selfed material, and rules out the theory of somatoplastic incompatibility. The behaviour of the antipodal cells of the embryo sac is not sufficiently different from normal to be of significance.