Volume 73, Issue 6
June 1971, pages 265-318
pp 265-272 June 1971
An assay of “wilt-sick” and “wilt-free” soils from cotton growing areas revealed the fungistatic nature of the latter soil to the wilt pathogenFusarium vasinfectum Atk. Screening of the soils for antibiotic producers, revealed that the “wilt-free” soil harbours far more microorganisms antagonistic to the fungus than the other, leading to enhanced “antibiotic index” and “antibiotic value” over the other soil. Among the microorganisms isolated from these soils, actinomycetes were the most potent antagonists.
pp 273-284 June 1971
A method was standardized for conducting pathogenicity ofFusarium vasinfectum Atk., on cotton, using spore suspension instead of conventional soil-oat inoculum. Spore load higher than an optimum seemed to decrease percentage wilt. The spores in high concentrations failed to germinate in glass-distilled water, soil extract and in soil. This apears to be due to some water-soluble self-inhibitory principle released by the spores. This principle might be responsible for the observed decrease in percentage wilt at the higher spore inoculum levels.
pp 285-289 June 1971
Somatic and meiotic chromosome numbers in 13 species ofIschaemum and two species ofSehima have been reported. Most of these numbers either constitute new reports or a revision of the earlier reports. Basic chromosome number seemed to be 10 inIschaemum andSehima with incidence of polyploidy ranging from diploid to hexaploid forms inIschaemum and diploid to tetraploid forms inSehima.
pp 290-302 June 1971
1. The detailed morphological structure of neurosecretory cells inLaevicaulis is given. There are two types of cells: cell type A is pyriform ranging from 83 to 133 µ in length, whereas cell type B is oval and is 49 to 66 µ in length. In both the cell types axonal transport of the secretory material is noticed. Both the cell types are PAS negative and positive for proteins and lipids.
2. Histological structure of the optic tentacle reveals that it consists of three types of neurosecretory cells of which the collar cells are situated around the central ganglia while the others are laterally down the sides of dermo-muscular wall. They are PAS positive and sudanophilic.
3. Cell type B showed a distinct annual cycle of activity which is correlated with the annual reproductive cycle ofLaevicaulis.
4. The effect of cutting the tentacles showed that number of eggs was increased in optic tentacles-cut animals. The tentacle homogenate injected animals showed no increase in number of eggs but the brain homogenate injected animals showed considerable increase in the number of eggs.
5. The amount of neurosecretory material in cell type A decreased from lower to higher salt concentrations. It may conclude that cell type A plays an important role in water balance as anti-diuretic factor.
pp 303-310 June 1971
The paper deals with the revision of the genusOmmatobrephus Nicoll, 1914 based on the study of the different type specimens and a large number of collections from different hosts and localities. This genus consists of four species; generotypeO. singularis Nicoll, 1914;O. lobatum Mehra, 1928 with many synonyms;O. megacetabulus Simha, 1958 andO. bengalensis Mukherjee and Ghosh, 1968.
pp 311-318 June 1971