On the hereditary transmission of microstructures of testa in reciprocal crosses between Linaria vulgaris and L. repens

Scanning electron microscopic studies of seeds from mother plants of Linaria vulgaris (L.) M iller and L inaria repens (L.) M iller (Scrophulariaceae) after reciprocal crossing, disclose the species seed characters of the mother plant as regards gross morphology such as the form of the wings and of the seed bodies. The male genomes have, however, an apparent influence on the microstructures of the seed coat. The nature of this influence of growth‐affecting substances of male origin on the maternal integuments is discussed. The term extragerminal male induction is proposed for the interaction between the endosperm and embryonic and other adjacent tissues of the seed, causing phenotypic expressions characteristic of the father plant.