ABSTRACT

The genus Origanum (Lamiaceae) includes 39 species widely distributed in the Mediterranean region (Vokou et al., 1993). The species Origanum vulgare predominates in occurrence, while Origanum dictamnus is endemic of the island of Crete in southern Greece. The plants are perennial herbs spontaneously growing in calcareous substrates. One of the striking morphological characteristics of the Origanum plants is the presence of glandular and nonglandular hairs covering the aerial organs. Both types of hairs originate from epidermal (protodermal) cells. Every epidermal cell, according to Netolitzky (1932), practically possesses the potentiality to develop into a hair. A number of external and internal factors, however, determine which ones of the typical epidermal cells will develop into hairs, and furthermore, which morphological pattern they will follow.