ROSELLINIA LIMONIISPORA: NUCLEAR CHANGES IN THE DEVELOPING ASCUS

Abstract

The nuclear cycle in the developing ascus of Rosellinia limoniispora, as revealed in aceto-orcein and acetocarmine smears, follows the general pattern for the higher Ascomycetes: crozier formation, early synapsis of homologous chromosomes in the fusion nucleus followed by nucleolar fusion, rapid elongation of chromosomes and ascus up to late pachytene of prophase I followed by contraction of the chromosomes and nucleolus, and the formation of eight nuclei as a result of two meiotic and one mitotic divisions. The orientation of nuclei in divisions II and III is haphazard. Ascospore delimitation is by simple cleavage of the cytoplasm; no centriole – astral ray mechanism was observed. A nuclear division occurs in each young ascospore, one daughter nucleus being cut off into a cell and degenerating.