• Volume 78, Issue 4

October 1973,   pages  143-193

• Effect of various carbon and nitrogen sources on the growth and sporulation ofMicroxyphiella hibiscifolia

The carbon and nitrogen nutrition ofMicroxyphiella hibiscifolia Bat., Nasc., and Cif., isolated from the leaves of cotton (Gossypium hirsutum L.), was studied at 28° C for 14 days at pH 4·0. Out of forty-one carbon compounds tested, the pathogen showed excellent growth on dextrose, sucrose, starch, raffinose and maltose; good on inulin; fair on melibiose and galactose; and poor or no growth on rest of the carbon compounds. The pathogen showed excellent sporulation on all the carbohydrates, in general. Out of thirty-three nitrogen compounds tested, the pathogen showed excellent growth on peptone, asparagine, proline, ammonium oxalate, yeast extract, ammonium phosphate, ammonium sulphate; good on ammonium chloride, serine, ammonium nitrate, urea, sodium nitrate, potassium nitrate, histidine mono HCl and histidine di HCl; fair on glutamic acid, lysine mono HCl, arginine mono HCl, threonine, nor-valine and glycine; and poor or no growth on rest of the nitrogen compounds. The pathogen showed excellent or good sporulation, in general, on all the nitrogen compounds. The utilisation of potassium nitrite was conditioned by the pH of the medium.

• Some biophysical considerations of insect respiration

Problems posed in insect respiration from the time tracheae undergo pneumatisation and conduct oxygen to the respiratory tissues have been reviewed. The special architecture of the tracheae and their role in gas transport has been critically analysed. The entire respiratory apparatus is designed for thermoregulation. Tracheae are compared with coil reflux condensers which function not only to avoid vapour loss but also act as the principal coolants in the organisms which produce heat at a rate of 7·3 ml O2/gm/min (N.T.P.). The kinetic process of gas transport along fine tracheal tubes follows Poiseuille’s law. The fluidity$$\left( {Poise^{ - 1} , or/\left| {{{cm} \over {\sec }}} \right|{{dyne} \over {cm}}} \right)$$ decreases with rise in temperature. In addition, it has recently been pointed out that heat loss is regulated by control of blood circulation (Heinrich, 1970, 1971). Therefore, it is plausible that the part of the heat is transferred by conduction as given by Fourier’s law.$$Q = U_1 A_1 {{At} \over {Ax}}.$$

All the processes of heat conduction are often surpassed by convection, radiation and vaporisation. Since increased ventilation brings about forced convection, the Reynold’s number or Grashoff number also increases. The silvery glistening tracheae provide excellent reflecting and radiating surface and the rate of radiation follows Stephan-Boltzmann’s rule. Some provocative fresh reflections on the new hypothesis of thermoregulatory role of insect respiratory system has been advanced with support from well-established physical laws.

• Fossil fishes from the Inter-trappean beds of Surendranagar District, Saurashtra

The present paper gives for the first time a detailed account of the fossil fishes from the Inter-trappean beds of Bamanbor and Ninania Surendranagar District, Saurashtra. This study has revealed the prosence of two new generaHoraclupea andPalaeopristolepis represented here by one species of each. The other remaining form,Perca sp. cf.P. angusta Agassiz is based on skeletal remains. The Inter-trappean beds yielding this fish fauna are considered to be of freshwater lacustrine nature and of Palaeocene or perhaps Lower Eocene age.

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