Gametogenesis and fertilisation in certain monocotyledons

Abstract

At the outset of the investigation, it was hoped to elucidate details of meiosis and fertilisation in dioecious and monoecious monocotyledons, with especial reference to the possible presence of sex chromosomes. The chromosomes of the dioecious and monoecious forms examined however, have not lent themselves to such a study, whereas the chromosomes of the hermaphrodite Scilla nonscripta, have proved especially interesting. This plant has therefore latterly been studied almost to the exclusion of others. Scilla nonscripta. The chromosomes during mitosis and meiosis are conceived as always consisting of at least two regularly intertwined spiral chromonemata. An attempt has been made to harmonise this conception, already held by many writers for mitosis, with the appearances observed at meiosis.At fertilisation, the egg nucleus is usually resting and the male nucleus is in a condition corresponding to late prophase. The membrane between the two nuclei breaks down and the reticulum from the male nucleus gradually spreads through the egg nucleus. The fusion of the second male nucleus with the two polar nuclei is similar. In all the divisions of the endosperm nuclei studied, the chromosome complements from the male and polar nucleiremain separate, but a mingling of the two chromosome complements in the nucleus of the embryo begins to occur after the first division.Hydrocharis morsus-ranae. The development of the flower buds has been traced, to find if the reputed lack of seeds in this country is due to any structural peculiarity. In the course of the investigation, however, seeds have been set and the significance of this is discussed. The problem of dioecism and monoecism in the plant has also been investigated. Other Monocotyledons. Five other monocotyledons have been examined, but have contributed little of special interest.