Anatomical investigations on the genus Origanum L. (Labiatae) growing in Turkey

The number of taxa belonging to the genus Origanum, commonly used asoregano, reached to 25 with new additions in Turkey. In particular, there aredifficulties in distinguishing closely allied taxa. A detailed study has been carried outin order to distinguishing these taxa according to anatomical characteristics.In this study, 24 taxa of Origanum naturally growing in Turkey, is examinedanatomically. Cross-sections taken from the stem and leaves are illustrated.Anatomical features characters that are useful in distinguishing between taxaare covering hairs, glandular hairs, upper and lower epidermis shape, cell number,size, type of stomata, number of neighboring cells of stomata, crystal, cuticleoverhang, width of vascular bundle, supporting tissue cell type, the number of layerof support tissue.For all Origanum species growing in Turkey, to support the morphologicaldifferentiation key, the alternative distinctive anatomical key is established. It isespecially expected to be useful for the determination of specimens were incompletecollected in terms of morphological characters.Keywords: anatomy, Labiatae, oregano, Origanum,Türkiye