Volume 41, Issue 5
May 1955, pages 189-239
pp 189-195 May 1955
pp 196-208 May 1955
P. clandestinum consists of two varieties,viz., Kabete andRongai. TheRongai variety showed abnormalities of micro-sporogenesis resulting in poor pollen and non-exserted stamens and did not form seed when isolated although it showed fertility on the female side by forming seed when it had access to pollen. TheKabete variety had normal pollen and exserted anthers and formed good seed. Seeds obtained by hybridising the two varieties using theRongai as the female parent, gave rise to maternal plants and hybrids with viable pollen and exserted anthers, showing not only the recessiveness of the male sterility inRongai, but also indicating facultative apomixis. This indication was confirmed by cytological evidence based on a chromosomal count showing the formation of haploid and aposporic embryo sacs. Embryo formation is normal inKabete and is preceded by endosperm formation. Polyembryony occurs.
pp 209-219 May 1955
A study of 30 strains ofAcetobacter species from diverse sources such as air, soil, various fruits, fermented liquors and animal excreta was attempted. By a detailed characterization of the isolates, they could be divided into 5 groups and identified as species ofA. aceti, A. xylinum, A. pasteurianum, A. melanogenum, A. industrium, A. oxydans, A. aceti viscosum, A. aceti roseum, A. rancens and their variants. Detailed descriptions of the less known species are presented to supplement the information available in appendix to the genus given in theBergey’s Manual. The description of a group of 6 strains which possess the unusual property of fermenting several carbohydrates with the production of acid and gas—a property not thus far ascribed toAcetobacter species—is also given.
pp 220-226 May 1955
Cytological observations on the naturally occurring mutant gram have been described. The mutant was found to be an autotetraploid with 2n=32. Some seedlings with one extra chromosome were observed. Occurrence of such extra chromosomes is common in the progenies of autotetraploids.
Detailed and critical analysis of morphology of the individual chromosomes in the somatic complements of the diploid as well as tetraploid types has been given for the first time.
Decrease in size of chromosomes with increase in chromosome number was not observed in the case of the mutant studied.
The coefficient of multivalency was found to be fairly high in the mutant which indicated that continuous selection in the selfed progenies would be necessary for some years.
Maximum germination of pollen grain was obtained on 12% sugar solution in the case of tetraploid gram and on 71/2% in the case of diploid gram which indicates that the tetraploid gram has higher osmotic pressure indicative of higher concentration of water-soluble cell contents.
pp 227-239 May 1955