Mitosis and Cytokinesis in Sessile Sporangium Oftrentepohlia Aurea(chlorophyceae)1

An ultrastructure study of mitosis and cytokinesis in the sessile sporangium ofTrentepohlia aurea(L.) Mart, was made to clarify the phylogenetic position of the alga. Mitosis was closed and centric at late anphase with cytokinesis involving the production of cleavage membranes by dictyasames between the numerous, well‐separated daughter nuclei. Neither phycoplast nor phragmoplast microtubules were observed during cytokinesis. The lack of phycoplast microtubules and the presence of multilayered structures in flagellated cells suggestTrentepohliais phylogenetically related to those green algae thought to have given rise to the land plants. The primitive type of mitosis and the lack of microbodies suggest that the ancestors ofTrentepohliamay have branched off from this line relatively early.