Volume 71, Issue 5
May 1970, pages 177-220
pp 177-192 May 1970
The authors have recorded 33 species of Chaetognaths belonging to four pelagic genera (Sagitta Quoy and Gaimard;Pterosagitta Costa;Krohnitta Ritter-Zahony; andEukrohnia Ritter-Zahony) and one benthic genus (Spadella Langerhans), from the Indian Ocean and contiguous Seas. The dependable specific characters useful in identification are discussed and an illustrated key to the identification of the genera and the species is provided.
pp 193-203 May 1970
Seasonal variations in a natural population ofDaphnia carinata was carried out for a period of one year in a natural freshwater pond. Fluctuations in the density of this cladocera was found to be directly related to the fluctuations in the available food. The rise in water level and occurrence of ephippial eggs were correlated. Major components of the population were parthenogenetic females and ephippial eggs. Ephippial females and males were recorded in very low numbers for a short duration. The probable cause attributed to the production of males are crowding of females and reduction of available food material. Animals having a length of 1·6–2·0 mm. formed the predominant group in the population. The occurrence of most of the length groups in almost all the collections has been attributed to the continuous addition of young ones from the parthenogenetic females and by the hatching of ephippial eggs. While events in the life-cycle of this tropical species are similar to those observed in cladocera from other climatic regions, the occurrence of ephippial eggs and their probable role in the population build up was found to be unique for this species.
pp 204-212 May 1970
The investigations embodied in the paper describe different methods of culturing tissues ofTectona grandis (teak),Artocarpus heterophyllus (jack),Morus alba (mulberry) andPopulus nigra (poplar). Of these, teak, jack and mulberry tissues have been established in culture for the first time. Teak, mulberry and poplar tissues grow well on Murashige and Skoog’s medium containing 1·0 ppm glycine, while jack tissue grows well on Blaydes’ medium. The tissues of teak, grown on Marashige and Skoog’s medium containing 3·2 mg. glycine and gibberellic acid, have good pigmentation. Jack tissue requires a specific higher temperature (30° C.) for its growth.
pp 213-220 May 1970
The flowers are pentamerous. The staminal bundles arise conjointly with the sepal medians and the petal bundle with adjacent sepal laterals. The dorsal bundles of the carpel remain indistinct although. The anthers inRibes are dithecous and show a glandular tapetum. The pollen grains are dimorphic and are shed at bicelled stage. The ovules are anatropous, bitegmic and crassinucellate. The development of embryo sac conforms toPolygonum type. Two cases of twin tetrads of megaspores (False Polyembryony) have also been reported. Transfer of the genus into a new family of its own is not favoured.