NUCLEAR DIVISION IN CONIDIA AND HYPHAE OFVERTICILLIUM ALBO-ATRUM

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Abstract
The mode of division of vegetative nuclei in the conidia and hyphae of Verticillium albo-atrum has been studied using HCl/Giemsa, Fuelgen and Acid Fuchsin staining methods.The conidial nucleus assumes a horse-shoe shape before forming a ringed constellation in which a number of chromosomes is joined by a fine thread. Chromosome division occurs resulting in closely associated double rings which eventually separate.In hyphae, a highly condensed nuclear configuration in which the chromosomes have already duplicated is drawn out by a rapidly enlongating spindle fibre (probably produced by centriolar division). A double stranded filament is formed composed of two parallel rows of chromosomes connected by fine threads lying on either side of the fibre. The axis and role of this fibre is discussed in relation to the transverse intrachromosomal spindle concept. The possibility that double stranded nuclei represent diploid stages with significance for mitotic recombination is discounted until further evidence is forthcoming. Daughter nuclei are formed after a transvrese break.Nucleoli arise de novo. A haploid count of n = 4 is suggested.Vegetative nuclear division in this organism, and many other fungi, has little in common with classical mitosis.