Amer. J. Bot. 60(6): 524-528. 1973
Charles T. Hammond & Paul G. Mahlberg
Department of Plant Sciences, Indiana University, Bloomington 47401
Keywords: Cannabis sativa, Cannabaceae, Cannabinoid, Individual Glands, Trichome
Three distinct types of glandular hairs of increasing morphological complexity which occur on flowering tops of Cannabis sativa L. (marihuana) are described from scanning electron microscopy. These gland types-termed bulbous, capitate-sessile, and capitate-stalked, described from pistillate plants-occur in greatest abundance on the outer surface of bracts ensheathing the ovary. Bulbous and capitate-sessile glands, which arise at an early stage in bract development, are scattered over the bract surface. Mature bulbous glands have a small swollen head on a short stalk, whereas capitate-sessile glands have a large globular head attached directly to the bract surface. Because of their numbers and large size, capitate-sessile glands are the most conspicuous gland type during the early phase of bract development. Capitate-stalked glands, which have a large globular head on a tall, multicellular stalk, differentiate during subsequent bract development. These stalked glands arise first along the bracteal veins and then over the entire bract surface. A voluminous, fluid secretory product accumulates in the glandular head of all three types. These glands are believed to be a primary site of localization of the marihuana hallucinogen, tetrahydrocannabinol.