Volume 77, Issue 6
June 1973, pages 225-275
pp 225-233 June 1973
The paper describes four juvenile stages referable to the apodous holothurianPatinapta ooplax (Marenzeller), collected in the intertidal sands of Andaman Islands. A comparison of these juvenile stages with adult specimens known in literature, suggests that the present specimens represent successive growth stages in the development of the species. A preliminary account on autecology of these animals is given.
pp 234-242 June 1973
The embryo sac development in cultivated species of rice and its autotetraploid forms has been investigated in detail. The investigation brought out, the causes for the low seed set in the autotetraploid forms as owing to the defects in the development of embryo sac in the differentiation and development of zygotes. Frequently post-fertilisation defects have also been met with. Despite the course of embryogenesis being similar in the diploid and autotetraploid forms, the differences in seed fertility in autotetraploids are considered te be due largely to gametic sterility and also due to the zygotic inviability, abortion and degeneration.
pp 243-246 June 1973
A new species ofEimeria (Protozoa: Eimeriidae) infesting the small intestine of a Chiroptera-Taphozous melanopogon Temminek, collected from Andaman Islands is described in this paper. The criteria for considering it as new species to science are given and these have been compared with the five species ofEimeria hitherto described from Chiropteran hosts. This seems to be the first record of a coccidium from a Chiropteran host in India.
pp 247-251 June 1973
In the 12 species ofIschaemum and two ofSehima studied, anthesis and dehiscence take place between 9 and 10a.m. and again between 4 and 5p.m. each day. Periods and modes of boot and panicle emergence as also the anthesis and dehiscence, however, vary in some detail in different species and their biotypes. These have been presented. Such data are of considerable value in breeding as also in seed production.
pp 252-263 June 1973
Development of microsporangium, male gametophyte, megasporangium, megagametophyte, endosperm, embryo, pericarp and seed coat inCyperus alopecuroides has been investigated. The anther wall consists of the epidermis, fibrous endothecium, a middle layer and glandular tapetum whose cells remain uninucleate throughout. The four nuclei formed after meiosis take an excentric position near the inner end of the microspore mother cell. One of the four nuclei increases in size and moves towards the center of the microspore mother cell and functions further, while the other three remain small and degenerate later. A simultaneous type of cytokinesis results in the formation of a thin cell wall separating the functional nucleus from the non-functional nuclei and similar walls separate the latter from each other. The pollen grains are shed at the three-celled stage. The gynoecium is bicarpellary, syncarpous and the ovary is unilocular with a single, basal, anatropous, bitegminal and crassinucellar ovule. The micropyle is formed by the inner integument only. Some of the funicular cells near the micropyle elongate and function as an obturator. After fertilization, a well-developed hypostase becomes differentiated at the chalazal region of the ovule just above the funicular vascular strand. The development of the megagametophyte conforms to the Polygonum type. The endosperm is of the Nuclear type and the embryo development corresponds to the Juncus variation of the Onagrad type (Johansen, 1950). Pericarp is four-layered. All the four layers become thick-walled in the mature fruit. Seed coat is two-layered and is formed by both the inner and the outer integuments. Seed coat is free from pericarp.
pp 264-275 June 1973
In leguminous weeds,Cassia tora L. andCrotalaria medicaginea Lamk., the ageing of the plants was accompanied by a quantitative increase in the rhizosphere fungal population which reached the maximum level at the senescent stage of the plants when the moisture content of the soil had fallen significantly. Concomitant with these phenomena was the decrease in the amino acids and sugars contained in the root exudates. Th role of root exudates, moribund root cells and the moisture content of the soil in bringing about these changes in the mycoflora are discussed.