I. MORPHOLOGICAL NUTLET CHARACTERISTICS OF SOME LAMIACEAE TAXA IN SAUDI ARABIA AND THEIR TAXONOMIC SIGNIFICANCE

The nutlet characters in the Lamiaceae are of great taxonomic significance. Macro and micro morphology nutlets of 23 taxa belonging to 12 genera of Lamiaceae from Al-Taif, Saudi Arabia have been studied for the first time by both light and scanning electron microscope. Observations revealed that nutlet color, shape, size, presence of areole are of limited taxonomic value. However the pericarp sculpturing are the most important diagnostic characters for differentiating the species through a constructed key. Three main distinct types of nutlets sculpture can be distinguished; smooth, partly sculptured and sculptured, within these types 12 subtypes are also recognized (reticulate, reticulate-foveate alveolate, granulate, rugose-scalariform, favulariate, protuberance, colliculate, ruminate, ocellate, verrucate and tuberculate). The relationships between the studied taxa were demonstrated as a phenogram.