Nutlet size, shape and surface ornamentation in 14 Onosma species (Boraginaceae)

Nutlets of 14 species of Onosma L. in Turkey were examined with scanning electron microscope. Nutlet (mericarp) morphology of the examined specimens exhibits some variation in shape and size. Nutlets of species vary in the range 2.5–6 ´ 2–4.5 mm. The studied nutlet surfaces show some variations. According to surface ornamentations 5 types were defined and illustrated: Type 1 Ruminate type), Type 2, Type 3 (Rugose-type), Type 4(Reticulate-type) and Type 5 (Pusticulate-type). The reticulate is the most common type in the examined species. Six of the species observed belong to the reticulate type, i.e. O. papillosum, O. lycaonicum, O. caerulescens, O. rascheyanum, O. mersinana and O. riedliana. In addition, the nutlet features of O. papillosum H. Riedl and O. lycaonicum Hub.-Mor., previously unpublished, are given for the first time here in detail. It is clear that external nutlet characteristics could especially help in the classification of the species of the complex genus Onosma in the future