VARIATIONS OF THE SURFACE SCULPTURE AND CELL-WALL ULTRASTRUCTURE OF THE ZYGOSPORES IN CHLAMYDOMONAS-GEITLERI (CHLOROPHYTA)

The superficial cell wall ornamentation in the zygospores of the alga Chlamydomonas geitleri Ettl (Chlorophyta) is formed by thickenings of the cell wall which are shaped into a network of anastomosing ribs, so metimes with local wart-like protuberances. Clearly different sculptur e patterns (given by presence, arrangement and/or morphological modifi cation of sculpture elements) were accompanied by many transient forms . Sculpture variations occurred even in clonal cultures. In the zygosp ore cell wall of C geitleri, the inner, outer and middle layer can be distinguished from the morphological point of view. The relatively thi n outer (sporopollenin) layer covers the whole surface of the zygospor e wall. The thicker inner layer adhering to the zygospore protoplast f orms, either solely or together with the middle layer (possessing a fi ne meshwork substructure), variously shaped thickening of the zygospor e cell wall. Discussed are the ultrastructural morphology of the cell wall in Chlamydomonas zygospores, the striking similarity of the cell wall ultrastructure of zygospores in C geitleri to the ultrastructure of the cell wall of vegetative cells in some green algae (subfamily Sc otiellocystoideae), as well as the extensive morphological variability of the zygospore wall sculpture in C geitleri and its species specifi city.