Abstract
A detailed cytological study of tapetum tissue accompanied by micrographic confirmation has been performed in a high number of cells in the four plant species, Launaea mucronata, Picris babylonica, Senecio glaucus and Sonchus oleraceus. While in these species, all tapetal cells were binucleated as a result of an obligatory first acytokinetic mitosis, in two species this was followed by a second division forming tetranucleated cells and in the other two species a further third division followed to form octanucleated cells. Existence of variable percentages of tapetal cells with other numbers of nuclei has been documented and interpreted. Similarly endopolyploidy phenomena was found to be of general occurrence in all four species. Its possible origin and significance for the developing microspores has been stipulated. Diagrammatic illustrations are insinuated to elucidate the possible origin of nuclei having variable ploidy levels and sizes. These illustrations have been based mainly on fusion of neighboring chromosomal groups, an inhibition of spindle formation or incidence of persisting chromatid bridges which could prevent proper separation of chromatids.
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