Mitosis, Cytokinesis, the Distribution of Plasmodesmata, and Other Cytological Characteristics in the Ulotrichales, Ulvales, and Chaetophorales: Phylogenetic and Taxonomic Considerations1

SUMMARY The results of previous research and a present survey of some of the cytological characteristics of 18 additional genera and 34 additional species are presented and discussed from the viewpoint of phylogenetic and taxonomic significance. A preliminary attempt is made to place these, algae, in 4 orders on the basis of comparative cytology, and in particular on the basis of variation in mitosis and cytokinesis and the distribution of plasmodesmata. Consideration is given to the evolution of the phragmoplast and to the hypothesis that the Chaetophorales are related to the ancestry of land plants.