Volume 55, Issue 6
June 1962, pages 285-319
pp 285-289 June 1962
pp 290-295 June 1962
The results of some preliminary observations onBipolaris sorokiniana (=Helminthosporium sativum) which causes foot rot in wheat are reported here. By direct microscopic examination of the rhizosphere it was seen that the pathogen not only grew vigorously on the rhizoplane but also sporulated in abundance in the rhizosphere. A method is described for quantitative assessment of the spore load in the rhizosphere, expressed as number of spores per gram of rhizosphere soil. Using this method, a gradual decrease in spore load in the rhizosphere of wheat seedlings with increasing age was observed. Histological study of infected and uninfected roots showed intra-cellular development of the fungal hyphæ in one or two outer layers of the cortex in the case of the infected root. Fungal penetration deeper into the cortex was not seen. Disintegration of the cortical cells was evident and is indicative of degradation by enzymes of the pathogen.
pp 296-301 June 1962
The origin and development of air chambers in four monocotyledons studied fall under three categories:
(i) where the chambers arise and develop lysigenously, (ii) where they arise schizogenously and enlarge lysigenously, and (iii) where the chambers arise and increase in size schizogenously.
The causes to explain the formation of air chambers as given by earlier investigators have been discussed with reference to the materials studied.
pp 302-306 June 1962
Rhizopus homothallus Hesseltine, a homothallic species ofRhizopus Ehrenberg, has been isolated from cultivated and river bank soils of Lucknow. Preliminary investigations indicate it to be a natural inhabitant of sandy soils with low moisture content.
pp 307-319 June 1962
The physical, chemical and microscopic changes brought about by the intrusion of a mica-peridotite dyke in the Dishergarh seam have been investigated.
The vitrain bands show distortion, folding and fading of lustre. Near the contact the coal is converted into ‘jhāmā’ which shows columnar structure.
The chemical characteristics of the coal show more rapid changes on approaching the dyke. The coal has been affected up to a distance of 8 feet from the contact or slightly beyond, but is practically unaltered at a distance of 11 feet.
The microstructures of fusain have not been affected. Vacuoles and cracks appear in the vitrain bands which increase in number and size as the dyke is approached. These are now filled with secondary mineral matter.