B. Papp szerk.: Studia Botanica Hungarica 35. 2004 (Budapest, 2004)

Wojtal, A.; Buczkó, Krisztina: Comparative study of Navicula hasta and N. rakowskae: their morphology and distribution

opinion, designation of a neotype or at least lectotypification of N. hasta should be made. The detailed LM and SEM studies of valve morphology of N. hasta (from Bodos) and N. rakowskae under the light microscope and scanning electron microscope showed that the similarities between these two species are mainly in length, width and raphe structure. Other features e.g. valve outline, striae density, and their density, shape of axial area, structure of the external valve surface are different. The study confirms also differences in density of lineolae between N. hasta and N. rakowskae, stated by Lange-Bertalot as separating criteria. On the other hand N. rakowskae should be compared with the recently lectotypified N. hasta var. gracilis Skvortzow (OHTSUKA and TUJ1

2002), known from recent material from Japan. In the course of investigating the distribution of N. hasta we have found that numerous documented reports actually relate to other taxa of the genus Navicula. In Poland a description of Navicula hasta was published in Polish by SlEMINSKA in 1963. Since then, the taxon has been reported from a few scattered localities as recent species (e.g. CHUDYBA 1979, KADLUBOWSKA 1985, KALINOWSKAKUCHARSKA and LlGOWSKI 1976, OLEJNICZAK and SZELAG 1979, KALINOWSKA-KUCHARSKA 1984), but these reports were not supported and validated by any iconographie documentation. Of eight reports from Poland (from the Tatra Mountains, KAWECKA 1965, 1966) only two presumably concern Navicula hasta sensu lato. The observed specimens were similar to N. hasta documented by CLEVE-EULER in 1953 (pp. 135-136, fig. 774c), which according to LANGE-BERTALOT (2001) conforms to N. hasta covered by the protologue. The population of N. hasta reported by RAKOWSKA (1996) is at present separated as N. rakowskae. The results confirm significant morphological differences between N. hasta (sensu LANGE-BERTALOT 2001) and N. rakowskae. A revision of Navicula hasta should be made in the future. At that time additional information may become available for determining the validity of records in the literature. The authors are interested in recovering additional reports and comments for future use. Acknowledgement - Our thanks are due to Prof. Hiroyuki Tanaka (Chuoh Senior High School, Gunma, Japan) and Dr Taisuke Ohtsuka for providing data from Japan, Dr Christine Cocuyt for African data, Prof. Andrzej Witkowski, Dr Frithjof A.S. Sterrenburg, and Ass. Prof. Konrad Wotowski for very valuable suggestions and critical comments on the manuscript. This work was partly supported by the State Committee for Scientific Research (grant 2 P04G 098 26). This work became possible thanks to the kind co-operation between the Hungarian and Polish Academies of Science.