FRAGILARIAANDSYNEDRA(BACILLARIOPHYCEAE) A MORPHOLOGICAL AND ULTRASTRUCTURAL APPROACH

Abstract
In this paper we discuss and illustrate the morphological and ultrastructural features of several Fragilaria and Synedra representatives. These features are often very similar in the two genera, raising once again the question of generic circumscription. New observations are presented for: Fragilaria virescens var. subsalina f. oviformis, Synedra arctica, S. camtschatica and its var. finnmarchica, S. pulchella var. macrocephala, S.fulgens, and S. undulata. Ardissonia and Toxarium should be reinstated as genera because of distinct valve characters.