Comparative nuclear cytology of Coelastrum

Abstract

The nuclear cytology of two varieties of Coelastrum proboscideum and two strains of C. microporum is described. All four Coelastrum organisms possess low chromosome numbers. Coelastrum proboscideum var. gracile Vischer has six chromosomes; C. proboscideum var. dilatatum Vischer has four; C. microporum Naegeli (strain 280) has six; and C. microporum Naegeli (strain 281) has seven. Chromatin granules are observed in C. proboscideum var. gracile Vischer, C. proboscideum var. dilatatum Vischer, and C. microporum Naegeli (281) and their condensation leads to the formation of organized chromosomes. Chromatin threads are only observed in C. microporum Naegeli (280). It is evident that the four Coelastrum organisms are quite different in their chromosomal morphology and mitotic behavior. However, at present, it is not certain whether the chromosome numbers are the haploid or diploid numbers since sexual reproduction has not been confirmed and meiotic division has not been observed.