Leaf pubescence in Nicotiana is made up of organelles of complex shape and varied functions. Two major types of trichomes are observed : non glandular hairs or"tectors", and glandular hairs which can be further divided according to their length. The aromatic properties of tobacco are mostly due to the secretion of gummy exudates by certain hairs. Ultrastructure observations confirm that apical cells of both long and short glandular hairs have secretory characteristics; they also show the presence of chloroplasts in the glandular cells of the longer hairs and undifferentiated plasts in the glandular cells of the shorter hairs. A comparative study of the pilosity of Oriental tobacco and of dark tobacco reveals that there is no close relationship between the trichome density and the quantity of essential oil extracted. The proportion of long hairs (unicellular glands) is, however, always more important in the aromatic varieties.