ON FINE STRUCTURE OF CELL WALLS IN GENUS CLOSTERIUM (DESMIDIACEAE) WITH SPECIAL REFERENCE TO PORE SYSTEM

Electron microscopical investigations of 9 species of Closterium revealed that the cell wall in the genus Closterium is composed of an amorphous outer layer, the fibrillous primary wall and the fibrillous secondary wall. The outer layer is smooth or striated in longitudinal direction. The striation is caused by small grooves or ridges. The distance between the striae is in many cases below the limit of the resolving power of the light microscope. Therefore only 2 of 6 species studied, all of which have striated walls, are well known to be striated hitherto. -The secondary wall consists of bands of microfibrils oriented in parallel as it has been described for the Cosmarium type and Penium type. In Cl. lunula there were no bands of microfibrils. In all of the species of Closterium studied pores are evident. They are of a round, oval or longish form and their distribution is diffuse or in rows. The diameter of the pores was determined to be 25 nm to 95×190 nm. The construction of the pores differs from the well known of the Cosmarium type. The perforation is only situated in the outer layer whereas the fibrils of the primary wall and secondary wall run through the cone-shaped channel beneath and give it the appearance of a sieve. In the region of the pore channel an interfibrillous cementing substance seems to be lacking. A pore apparatus is absent, too. Cl. lunula has differently shaped pores. The observations were compared with the partly contrary declarations in the literature. The significance of the results is discussed with regard to taxonomic questions. © 1969 Springer-Verlag.