Distribution, taxonomy, nomenclature and molecular genetic data are presented for two closely related pairs of birch taxa: (1) dark-barked Betula pubescens var. sibakademica (Baran.) Kuzeneva (basionym B. sibakademica Baranov) and white-barked B. pubescens var. pubescens, and (2) dark-barked B. kotulae Zaverucha = B. pendula var. obscura (Kotula ex Fiek) Olšavská (basionym B. obscura Kotula ex Fiek, heterotypic synonym B. kotulae) and white-barked B. pendula, respectively. Using published data and sequences obtained in this study, it was found that, although these pairs can be distinguished not only by morphological characters but also by two diagnostic single nucleotide polymorphisms (SNPs) in the internal transcribed spacers ITS1 and ITS2, no sequence differences within each pair were detected. These results suggest that the colour of the bark cannot be used as a taxonomic trait at the species level, and the dark-barked birches within each pair should not be treated as separate species or varieties, but as forms, respectively. Therefore, we reassessed the taxonomic status of B. sibakademica and B. kotulae using morphological traits and molecular genetic markers and suggest that B. pubescens f. sibakademica (Baranov) Tarieiev comb. nov. and B. pendula f. obscura (Kotula ex Fiek) Tarieiev comb. nov. should be used for them, respectively. Betula pubescens f. sibakademica was described in Ukraine for the first time.

The article provides data about authentic materials of Betula (Betulaceae) names described from Ukraine and deposited at the National Herbarium of Ukraine (KW). For each taxon, its protologue, synonyms and text of the label are presented. We designate here lectotypes of Betula borysthenica Klokov, B. klokovii Zaverucha, and report the holotype of B. kotulae Zaverucha, and authentic materials of B. klokovii Zaverucha, B. polessica Ivchenko etc.

Iris pineticola Klokov (1950: 407) is considered a species endemic to Ukraine. It occurs in Zhytomyr, Kyiv, Chernihiv, Sumy, Vinnytsia, Cherkasy, Kirovohrad, Dnipropetrovsk, Poltava, Kharkiv, Donetsk, and Luhansk regions (oblasts in Ukrainian). It is listed in the Red Data Book of Ukraine (Ostapko 2009). According to the Red Data Book of Ukraine, its conservation status is Vulnerable.

Чорноморський ботанічний журнал-том 12, № 2 (2016) Мікроморфологічна характеристика (анатомічна структура листків та стебел, ультраструктура плодів, ультраскульптура пилкових зерен) Sonchus oleraceus L.