Key...132 Descriptions...133 6. Nomina dubia ...145 7. Species excludenda ...145 8. Index of collections...146 9. Index of taxonomic names...149 SUMMARY The present study deals with the systematics and taxonomy of the genus Origanum (Labiatae, Saturejeae). As this difficult genus was never before monographed, a revisional study was much needed. The data presented are mainly based on the study of herbarium specimens and in some cases of living ones. The picture was completed, as far as possible, with data from various literature sources. A short survey is given of the taxonomic history of Origanum, which goes back as far as Linnaeus, and shows that genus and species concepts of various authors have much differed. A morphological outline of Origanum is given, from which it can be concluded that most generic characters are rather variable. Origanum is characterized in the following ways.Medium sized, subshrubby Labiatae, rich in volatile oils, with subsessile, ovate, glandular punctate leaves and paniculate inflorescences; few flo- wered verticillasters arranged in (dense) spikes with distinct, often coloured, bracts; calyces variable: 5-toothed, subregular or 2-lipped or I-lipped, with developed or reduced teeth; corollas 2-lipped, sometimes saccate or flattened.
