Further Investigations on Xenia in Maize

Abstract

Probably few botanical discoveries of recent years have aroused more interest trian the remarkable observations of Nawaschin upon the fusion of one of the generative nuclei of the pollen tube with the definitive nucleus'of the embryo sac. Since further investigations have rendered it not improbable that the process is of general occurrence, its bearing upon some curious phenomena met with in hybrids is of great interest as affording an explanation, not only as to how hybrid embryos, but also how truly hybrid endosperms can be produced by crossing different races of plants. De Vries' beautiful observations upon maize, which were made almost simultaneously with those of Correns, have already formed the subject of an article in this journal, and they have recently been considerably extended by some experiments conducted by Webber¹ in America. As a result of his investigations. Webber concludes, in all cases in which the hybrid corn shows a change of colour, that this is due to the endosperm alone, the translucent pericarp retaining, as might have been theoretically anticipated, the character properly appertaining to the corn of the female parent. But in a large number of instances it was found that, although the embryo on germination showed that hybridisation had occurred, there was no evidence of the transference of the qualities of the male parent to the accompanying endosperm. On the other hand, in some hybrid corns the endosperm exhibited a spotted appearance, which might even (e.g. when Gilman Flint was crossed with Stowell's Evergreen) be restricted to only a portion of its substance. The author suggests that the former case might be explained as being the result of failure on the part of the generative nucleus to unite with any nucleus within the embryo sac. The spotted endosperms, on the other hand, might be due to an independent segmentation of the second pollen nucleus, which had failed to unite with the polar nuclei, in which case the portion of endosperm so arising might be expected to retain the characters of the male parent.