Lange-Bertalot, H., 1980
Lange-Bertalot, H. (1980). Zur systematischen Bewertung der bandförmigen Kolonien bei Navicula und Fragilaria. Kriterien für die Vereinigung von Synedra (subgen. Synedra) Ehrenberg mit Fragilaria Lyngbye. Nova Hedwigia 33: 723-787, 16 pls.
Maintaining Synedra, in particular Eusynedra , and Fragilaria as two distinct genera has not led to taxonomical clarity as was up to now generally assumed . On the contrary, the artificial separation of closely related taxa into different genera has decidedly impeded taxonomic progress . Instead of arriving at the sought for better order one rather achieves taxonomic disorder. The long suspected insufficiency of the unique decisive differential criterion, namely the potency of forming filamentous colonies, has now been proved as such beyond doubt. Frustules living singly or in band-like aggregations (linked by spines or otherwi se) and the possession of a distinct labiate process combined with apical pore fields occur in Fragilaria as weil as in heretofore undisputed Synedra species. Other differentiating character s are not detectable , neither in electron microscopic structure nor by ecolo_gical reactions . Moreover, for almost each of the more prominent Synedra species a congruent double in Fragilaria can be discovered. In addition it has been shown that a single population of Fragilaria vaucheriae can develop with or without or even with mere rudiment s of linking spines thus mediating between the classic Sy nedra vaucheriae and Fragilaria intermedia. S. amphicepha/a and another indeterminable Synedra population live attached singly or in radiate clusters but not in filament s despite of weil developed spines on tbe valve margins. These facts are by no means in consistency with our recent artificial classification . Therefore, at least all the prominent cosmopolitan species in Eusynedra with well-known morphology have to be transferred to Fragilaria under the rules of the ICBN. For tbe new combinations and synonyms see under Appendix .