Volume 56, Issue 6
December 1962, pages 329-376
pp 329-331 December 1962
The present paper deals with chromosomes ofDioscorea deltoidea 2n=20 and its induced tetraploid from 2n=40. The position ofD. deltoidea in relation to other rhizomatous species of Dioscorea of Asia and Europe and to the tuberous yams in cultivation is presented.
pp 332-338 December 1962
The root apex shows distinct initials for stele and columella in super-imposing tiers. Initials for cortex, protoderm and periphery of the cap are pericolumnar.
Shoot apex shows one tunica layer (Cuminum cyminum) and two tunica layers (Daucus, Carum, Coriandrum andFoeniculum).
Root vasculature and cotyledonary supply are related, being independent of the procambium of epicotyl.
Cotyledonary node shows six gaps, three related to each cotyledon, and is thus trilacunar.
pp 339-353 December 1962
In the present paper vascular anatomy of the flower of all the three Indian species of Pontederiaceae,viz., Monochoria hastaefolia Presl,Monochoria vaginalis Presl andEichhornia crassipes Solms is described.
The perianth is a three-traced organ. InEichhornia crassipes it is interesting since it shows a bifacial anatomy which indicates its phyllodic nature. Each stamen receives a single trace which is adnate for some distance with the median trace of the perianth. The appendages of the larger stamen ofMonochoria are merely the outgrowths of the filament.
The gynoecium is tricarpellary syncarpous and trilocular. The vascular supply constitute of six bundles—three dorsals and three placental strands. Apparently, the placentation is axile in all the species studied. Anatomical studies also support it in case ofEichhornia crassipes. But inMonochoria, anatomically the placentation is parietal which appears to have been derived from the axile.
The present investigation also gives some support to the view that each placenta is a double structure composed of two half-placentae.
pp 354-362 December 1962
M. aeruginosa, the common blue-green algae, forms a permanent bloom in the Roshanara tank, Delhi. It occurs with varying degrees of concentrations throughout the year.
A detailed study of the water chemistry of this tank which was carried out seasonally revealed that high temperature, high contents of bicarbonates, carbonates, chlorides, silicates and low redox potential have very little to do with the production of algal bloom. The chemical factors which seem to favour the growth of this alga are large quantities of organic matter present in water, high alkalinity and large concentration of phosphates and nitrates. This tank, being well sheltered by vegetation, offers little turbulence in water. Probably the stagnation caused in water is one of the most important physical factors to favour a permanent bloom ofM. aeruginosa.
pp 363-371 December 1962
1. Salinity tolerance and volume regulation in four species of polychaetes,viz., G. embranchiata, O. erimita, L. medusa andC. insecta have been studied.C. insecta showed lower mortality rates and greater powers of osmoregulation than those of the other three species of polychaetes.
2. The distribution of these polychaetes in the brackish-water zones of Adyar, Madras, have been explained in the light of their capacities for tolerance and volume regulation. The probable role of nephridia in the unusual behaviour ofG. embranchiata has been shown.
pp 372-376 December 1962