Absolute Configuration Analysis of the Flagellar Apparatus of Pterosperma Cristatum (Prasinophyceae) and Consideration of Its Phylogenetic Position¹

Pterosperma cristatum Schiller, a member of the Pra‐sinophyceae, was examined with light and electron microscopy with special attention on the absolute configuration of flagellar apparatus components and associated structures. This alga is characterized by asymmetrically arranged basal bodies, connecting fibers and microtubular roots. The microtubular root system is homologous with the cruciate root system, the so‐called X‐2‐X‐2 root system typical of non‐charophycean green algae. Two ducts are associated with microtubular roots. A similar flagellar apparatus and duct system was found in two other prasinophyte genera, Pyramimonas and Halosphaera. The close phylogenetic affinity of these three genera is discussed.