Contribution to the biosystematics of genus Lathyrus L. (Fabaceae, sect. Pratensis Bässler)... 467 Proceedings of the 2 nd Congress of Ecologists of Macedonia Introduction Genus Lathyrus L. (Fabaceae) belongs to tribe Vicieae (Adans.) DC. and comprises about 150 species dis- tributed chiefly in Europe, Asia and North America, extending to temperate South America and tropical East Africa (Polhill & Raven, 1981). In the Bulgarian flora the genus is represented by 29 species (Kozuharov, 1976; 1992). Two of them Lathyrus pratensis L. and L. hallersteinii Baumg. are related to section Pratensis Bässler. The section is characterized by the presence of one-paired leaflets, large stipules, unequally sagittate and yellow flow- ers. A typical feature is the presence of equally-shaped calyx-teeth (Bässler, 1966). Both species are closely similar in their morphologi- cal characteristics and often difficulties arise in their determination. This leads to problems in presenting the correct chorological information, especially for L. hallersteinii. This was the main reason of conduct- ing the present detailed investigation on sect. Praten- sis in Bulgaria. Material and Methods The information for the distribution of the investigat- ed species as well as of their macromorphological features are based on the available literature data and specimens deposited in the Herbaria of Sofia Univer- sity (SO) and Institute of Botany at Bulgarian Acade- my of Sciences (SOM), and in personal collection. CONTRIBUTION TO THE BIOSYSTEMATICS OF GENUS Lathyrus L. (Fabaceae, sect. Pratensis Bässler) IN BULGARIA Anita TOSHEVA Sofia University “St. Kliment Ohridski”, Faculty of Biology, Department of Botany, blvd. Dragan Tzankov 8, 1164 Sofia, Bulgaria, e- mail: anytosheva @mail.bg ABSTRACT Tosheva A.. (2004). Contribution to the biosystematics of genus Lathyrus L. (Fabaceae, sect. Pratensis Bässler) in Bulgaria. Proceedings of the 2 nd Congress of Ecologists of the Republic of Macedonia with International Participation, 25-29.10.2003, Ohrid. Special issues of Macedonian Ecological Society, Vol. 6, Skopje. Sect. Pratensis Bässler is represented by two species in the Bulgarian flora - Lathyrus pratensis L. and L. hallersteinii Baumg. Both species are closely similar in their morphological characteristics and often difficulties arise at their determination. The available data on the distribution and morphology of both species in Bulgaria are summarized and revised in the present investigation. The macromorphological complex of features distinguishing the species is discussed. New information about karyology and pollen morphology is presented. The distribution of L. hallersteinii in localities of the floristic regions Central Stara Planina Mts. And Pirin Mts. is verified and three new localities were established for the floristic regions Western Stara Planina Mts, Rila Mts. and Vitosha Mts. The distribution is indicated on an UTM Grid map of Bulgaria (Scale 1: 1 500 000) (Fig. 1). The macro- morphological comparison of the species is shown on Table 1. The ecological characteristics are after Davis (1970) and Kojic (1972). The area-diagnosis after Meusel et al. (1965) is also presented. The materials for karyological and pollen-morpho- logical studies are collected from natural localities. The vaucher specimens are deposited in the Herbari- um of Sofia University (SO). The karyotypes are investigated on metaphase plates prepared from root meristem of germinating seeds treated in hot hydrolysis and stained in chematoxilin after Gomory (Pearse, 1960). The chromosomal type is determined after the centromere index I c =s/s+l according to the classification proposed by Grif & Agapova (1986). The karyotypes and their composi- tion are shown on Fig. 2. The absolute chromosome length (Σs+l) and the ratio Xmax : Xmim is also indi- cated. Pollen is acetolysed according to the standard proce- dure (Erdtman, 1960). For LO microscopy slides are prepared by mounting the pollen in glycerol jelly. Six pollen-morphological characters are measured: P (po- lar diameter), E (equatorial diameter), colpus length, porus diameter, M (mesocolpium), A (apocolpium) and the P/E ratio. For SEM observation acetolysed pollen grains are coated as dry specimens with gold with the aid of a JEOL-JFC-1200 Coater. The micro- photographs are obtained with JEOL-JSM-5510 SEM.