Polish Botanical Journal 46(2): 161–167, 2001 NEW OR RARE SPECIES OF THE GENUS NAVICULA (BACILLARIOPHYCEAE) IN THE DIATOM FLORA OF POLAND AGATA WOJTAL Abstract: Diatoms (Bacillariophyceae) inhabiting different kinds of substrate including stone surfaces, mud, filamentous algae and submerged vascular plants in Kobylanka stream (Kraków-Cze ˛stochowa Upland) were studied by means of light and electron micro- scopy. Among numerous common species belonging to the genus Navicula Bory s.l., taxa new to the Polish diatom flora were observed, including N. aquaedurae Lange-Bert., N. bacilloides Hust., N. reichardtiana Lange-Bert. var. reichardtiana, N. tenelloides Hust., N. wiesneri Lange-Bert., and one rarely reported from Poland, N. joubaudii H. Germ. Key words: Bacillariophyceae, Navicula, taxonomy, stream ecology, Kraków-Cze ˛stochowa Upland, distribution Agata Wojtal, Department of Phycology, W. Szafer Institute of Botany, Polish Academy of Sciences, Lubicz 46, PL-31-512 Kraków, Poland; e-mail: wojtal@ib-pan.krakow.pl INTRODUCTION Diatoms represent the most diverse group of algae in lotic environments of the Kraków-Cze ˛stochowa Upland. Information about diatom taxa occurring in springs, streams, rivers and ponds in nature reserves and areas affected by human impacts have been published in more than 50 papers. About 600 diatom taxa have been identified from this area during almost 120 years of phycological studies. The diatoms reported as predominant species are usually cosmopolitan and common. This paper contains observations on some species of the genus Navicula Bory new to the Polish dia- tom flora or so far rarely recorded. None of the reported taxa were frequent in the studied material, but although they are probably of little ecological significance in populated environ- ments they are important for floristic studies. Among them are species rarely reported anywhere (e.g., Navicula bacilloides Hust.), and taxa that are opportunists of human interference in nature (e.g., N. reichardtiana Lange-Bert. var. reichard- tiana) and are becoming more and more common (Lange-Bertalot 1999). STUDY AREA The Kraków-Cze ˛stochowa Upland extends from the Carpathian foothills in the vicinity of Kraków in the south to the town of Cze ˛stochowa in the north (Fig. 1). The diatom flora was studied be- tween 1993–1997 in Kobylanka stream. It flows through a limestone area, is one of the numerous tributary streams of the Rudawa River in the Do- linki Krakowskie Landscape Park. The first sec- tion of the stream retains some of its natural charac- ter in the Dolina Kobylan ´ska valley, but beginning from Kobylany village it becomes increasingly af- fected by human activity. The most characteristic features of the stream are these: karstic springs, bottom with limestone gravel on more rapid stream sections, or mud in places where water flow is slow, cold water during summer and rela- tively warm during winter. It is 7300 m long, 40– 120 cm wide, 10–30 cm deep, and the velocity ranges from 10 to 18 cm/s -1 . The water tempera- ture was 6.2 o –9.0 o C (rarely higher – up to 16.0 o C). Conductivity during the study was medium,