The cytoplasm of Ae. ovata delays heading by 13 days on an average in common wheat varieties, whereas T. timopheevi cytoplasm did not show such effect. Ovata cytoplasm also increases plant height, number of tillers and number of spikelets per spike ; on the other hand nucleus substitution lines with timopheevi cytoplasrn did not deviate greately from the normals. The influence of two fertility-restoring genes, Rfc1 and Rf3, was strikingly identical.
