The Cytology of Mycosphaerella pinodes*

Abstract

The behaviour of nuclei during ascus and spore formation and maturation in  Mycosphaerella pinodes (Berk. & Blox.) Stone was studied by means of the HCl-Giemsa technique. The mechanisms of dikaryotization could not be determined but typical croziers were formed. Nuclear fusion occurred in the young ascus and was followed by four conventional successive divisions. At pachytene the chromosomes could be counted and measured. The haploid chromosome number was found to be 15. Ascospore delimitation could be seen at metaphase IV so that each spore is homokaryotic. Two nuclear divisions occurred in the ascospores so that each cell became quadrinucleate.