CELLULAR ORGANIZATION,MITOSIS, AND CYTOKINESIS IN THE ULOTRICHALEAN ALGA,KLEBSORMIDIUM1,2,3

Mitosis, cytokinesis, and cellular organization during interphase are described. Interphase cells possess a single microbody-like organdie which occurs between, and is appressed to, the chloroplast and nucleus. The microbody-like organelle divides during mitosis and. the division of the chloroplast. Anaphase is unusual in that chromosome-to-spindle pole distance remains constant even though the 2 groups of chromosomes become widely separated. When anaphase is half completed, a vacuole forms in the interzonal region and appears to be involved in further separation of the chromosomes. Vacuolar development is also involved with events of early interphase. The cytology of K. flaccidum is compared to those of Ulothrix fimbriata and Stigeoclonium helveticum. The comparison, does not support the present classification of the 3 species, and indicates the value of comparative fine structural studies in the classification of ulotrichalean algae.