Pollen morphology of Thymus sect. Serpyllum (Labiatae : Mentheae) in the Carpathians and Pannonia

The pollen size and exine structure of 11 Thymus species from the Carpathians and Pannonia were studied by light and scanning electron microscopy using image analysis. Of the taxa studied, T. serpyllum has the smallest pollen grains, and T. pulcherrimus the largest. The pollen grains of all 11 species are hexazonocolpate, varying in shape from suboblate to euprolate. The exine is bi-reticulate and scrobiculate. A correlation is found between pollen size and chromosome number. The value of pollen characters for taxonomic purposes and the position of the taxa studied within the framework of tribe Mentheae are discussed.