• Volume 73, Issue 3

      March 1971,   pages  105-154

    • Indole acetic acid synthesis in sea

      D Chandramohan

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      The bacteria, present on the surface ofEnteromorpha intestinalis cells and in sea-water, can synthesize indole acetic acid (IAA) from L-tryptophan. Its possible role in algal growth is discussed.

    • A contribution to the embryology of iridaceae

      K K Lakshmanan V J Philip

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      Embryological aspects ofSisyrinchium striatum andS. californicum are studied. The wall of the quadrilocular anther consists of an epidermis, fibrous endothecium, one or two middle layers and a glandular tapetum. The tapetum is of dual origin. Cytokinesis during microsporogenesis are simultaneous. The microspore tetrads are isobilateral or tetrahedral. Pollen grains are shed at two-celled stage. Emryo-sac is of the Polygonum type. Endosperm is Nuclear. The apical cell of the two-celled proembryo contributes to the development of the embryo proper and part of the suspensor. The basal cell which may or not divide forms the suspensor.

    • Egg production and growth inDaphnia carinata king

      P Navaneethakrishnan R George Michael

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      Under laboratory conditions,Daphnia carinata has five preadult and eight adult instars in a temperature range of 29° C to 31° C. During a mean life-span of 24 days it produces about 142·4 eggs. When the cumulative frequency of eggs are plotted as regression lines, the two tropical speciesDaphnia carinata andCeriodaphnia cornuta show faster rates in egg production than the temperateDaphnia pulex. This may be attributed to differences in temperature. The pattern of growth rate in this tropicalD. carinata and the arcticD. middendorffiana were very similar in being faster while that of the temperateD. pulex was gradual. It is suggested that the limiting effects of tropical and arctic environments on animal populations may be comparable.

    • A contribution to the floral anatomy ofNepenthes khasiana Hook F

      K Subramanyam L L Narayana

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      Two kinds of multicellular trichomes, glandular and non-glandular, occur on the abaxial side of the perianth lobes, androphore and ovary wall; sunken multicellular glands are generally present on the adaxial surface of the perianth lobes. The development of these trichomes and glands shows that they are epidermal in origin. The flowers are uni-sexual. The perianth is tetramerous and each perianth lobe is traversed by three bundles. The origin and distribution of the staminal traces recall the condition in fasciculate androecium. The ovary is tetralocular below and unilocular above. The placentae which lie along the septal radii receive the half ventrals of adjacent carpels but do not fuse to form common ventral bundles. Thus the placentation may be described as tending towards the parietal condition. The stigma is commissural.

    • Some observations on the biology and life-history ofNandus nandus (Hamilton)

      S Parameswaran S Radhakrishnan C Selvaraj

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      In Assam, the minor predatory fish,Nandus nandus (Hamilton), matures by the middle of March and its breeding season extends from late March to the middle of July. The sexes can be distinguished externally during the breeding season, by the difference in the general coloration. The mature ovarian eggs measure 0·595 to 0·663 mm in diameter. The fecundity of the fish (length range: 75 to 138 mm) ranged from 1,573 to 23,546.

      Mature fish were induced to breed by the administration of carp pituitary hormones and the life-history, from the first cleavage to 11·328 mm post-larva, was studied. The fertilized, swollen eggs, having an average diameter of 0·799 mm, are spherical, adhesive and yellowish in colour with a central, spherical oil globule. At a water temperature of 20·0 to 22·3°C, the period of incubation is about 36 to 37 hours. The newly hatched larva measuring 2·070 mm in length has three characteristic vertical bands and pigmented eyes. It is devoid of mouth and pectoral fins. In the four days’ old larva, measuring 3·291 mm in length, the yolk is completely absorbed. The fins are fully formed and all the adult characters attained, when the post-larva is about 19 days’ old and measures 11·328 mm in length.

      The fish has a planktonic feed in the post-larval stage. It is predominantly insectivorous and piscivorous in dietary habits in the juvenile and adult stages respectively. The predatory habit of the fish warrants its eradication from nursery ponds.

    • Beachrock and associated carbonate sediments on the Fifty Fathom Flat, a submarine terrace on the outer continental shelf off Bombay

      R R Nair

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      Beachrock and associated carbonate sediments were obtained by dredging and coring on the Fifty Fathom Flat, a submarine terrace at a depth of fifty fathoms (91·5 meters) on the outer continental shelf off Bombay. The beachrocks are iron stained calcarenites composed of oolites and skeletal material cemented together in a fine-grained carbonate matrix. Thin sections show that the rocks are oobiomicrite with a high grain to micrite ratio. The allochems are superficial oolites, skeletal matter and grapestone and pellet intraclasts all of which either charged with iron oxide or glauconitised. Associated sediments on the Flat are glauconitic sand, oolites and coral debris. The karstic topography which is evident from the echograms and the occurrence of beachrock implies that the Fifty Fathom Flat stood at sea-level, probably during the Pleistocene and is now submerged due to eustatic and/or tectonic causes.

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