The Journal of Indian Botany/Volume 1/September 1919/The Morphology of Rumex cripus
Dudgeon, Winfield. The Morphology of Rumex cripus, Bot. Gaz., LXVI 5, pp. 393—420, 7 figs.
In this paper the author gives a detailed account of the development and histology of the flower of Rumex crispus, as part of a study of the morphology of the whole plant. He finds that in well developed flowers the development of the organs and of the embryo-sac and pollen grains follows the course usual in dicotyledons, with only slight variations. In the ovule the archespore is the terminal cell (below the epidermis) of a definite axial row. It divides into an upper cell which forms a 4-celled cap, and a lower cell, the embryo-sac mother-cell. This divides into a linear or nearly linear axial tetrad, the lowest cell of which becomes the embryo-sac. The haploid chromosomes in the division of the mother cell are 32 in number. The chief interest in the paper lies in the author's account of the very widespread degenerations which occur at almost any stage in the growth of the floral organs. These degenerations may, he finds occur (a) in any or all of the anthers, at any stage from the spo rogenous initial to the mature pollen grain, and may involve only the sporogenous tissue and its products, or the entire anther; (b) in the ovary at any stage from the functioning megaspore to the maturing fruit, and may involve only the embryo-sac, or both embryo-sac and ovule, or the entire ovary; (c) in entire inflorescences. The degeneration is accompanied by, and probably caused by, the formation of a definite abscission layer across the peduncle, whereby the floral organs are cut off from nutriment, and is so common that functionally perfect flowers are rare. As a result of such degenerations four types of mature flowers are produced (a) physiologically staminate (the ovary being functionless) in which the pollen may or may not be functional; (b) physiologically ovulate, the stamens having been completely eliminated by degeneration; (c) bisporangiate, having both stamens and ovary functional (very rare); (d) completely sterile, having functionless ovary and stamens completely eliminated. The author discusses shortly the bearing of these facts on the origin of dicliny, which he is inclined to consider may be due in other species also to gradual degenerations, and not as Strasburgher supposed to excessive mutation, nor to an absence of one sex in the seed, as suggested by Hoffmann, nor to hybridisation as Jeffrey believed.
P. F. F.