Page:The Journal of Indian Botany.djvu/39

 Observations on Euglena Deses.— Rose BRACHER (" Observations on Euglena deses ". Annals of Botany, January 1919, has studied the effect of external factors like light, tidal flow and temperature changes on the movements of Euglena Deses. She finds that in darkness, at night or at the tidal time the Euglenae burrow under the surface of the mud. As for the temperature, the EuglensB are active at any temperature between 2'5° C. and 25° C, outside which movements are arrested. The optimum temperature isl5°C.

Cytology of Tetrahedron minimum. — A. Br.— G. M. Smith ("Cell- structure andautospore formation in Tetrahedron minimum, A. Br." Annals of Botany, October 1918) has published an illustrated account of the cell-structure and autospore formation in Tetrahedron minimum. The young cell contains a single nucleus and a pyrenoid. Repeated mitosis may result in 8 nuclei within a single cell. Autospores are formed by progressive cleavage, the nuclei increasing in number at the same time, resulting in four, eight, sixteen or thirty-two uni-nucleate proto-plasts, each of which finally becomes an autospore. The pyrenoid disappears after the first cleavage, new pyrenoids being formed de novo in the young autospores.

Conjugation of Zygogonium ericetorum. Kutz. — W. J. Hodgetts (New Phylologist, December 1918) has carefully studied the process of conjugation in Zygogonium ericetorum, His observations confirm De Bary's account of conjugation in this alga. Greater part of the protoplast passes into the protuberance and is there formed into a sort of gametangium by its cutting off a curved partition wall. Each gamete secretes a thin wall round itself. Thus, before fusion, each gamete is surrounded by a double investment. Inner walls become only locally absorbed during the fusion and unite to form a continuous membrane round the zygospore, which persists as the outermost layer of its wall. Azygospores were also observed. Relation of Z. ericetorum te Zygnema pachydermium West, is discussed and the writer supports the retention of the genus zygogonium on the basis proposed by De Bary (1858), and accepted by Mille (1897, 1909). S. L. G.

Morphology and Histology.

Dudgeon, Winfield. The Morphology of Ruoiex 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