Nutlet micromorphology of Turkish Stachys sect. Eriostomum (Lamiaceae) and its systematic implications

The nutlet morphology of 32 taxa of Stachys sect. Eriostomum (Lamiaceae) has been studied by scanning electron microscopy (SEM), and a detailed description of the nutlet morphological features of all examined taxa is provided. We found some groups within Stachys sect. Eriostomum that present nutlet micromorphological characters that appear to be useful in the species-level taxonomy. The basic shape of nutlets in most taxa is obovoid or +/- rounded and the size ranged between 1.5 and 3.0 mm in length and between 1.0 and 2.5 mm in width. Five basic types of sculpturing can be distinguished: reticulatetuberculate, reticulatesmooth, reticulateslightly furrowed, colliculatetuberculate, colliculatesmooth. The reticulate type is the most common among the studied species. The colliculate type is characteristic for S. minor and S. cretica subsp. vacillans. Subsection Spectabiles with reticulate-smooth/slightly furrowed sculpturing is easily distinguished from the other subsections. In addition, nutlet micromorphology is useful for separating the subspecies of S. cretica. The systematic and biological implications of the nutlet characteristics are briefly discussed.