Cannabis leaf. Coloured scanning electron micrograph (SEM) of part of a cannabis (Cannabis sativa) leaf. The leaf surface is covered with hair cells called lithocysts, which contain cystolyths (calcium carbonate crystals). Glandular cells called trichomes are also present on the leaf surface. These cells secrete a resin containing tetrahydrocannabinol. The hairs and the chemical are specialized defenses against herbivores. When dried, the leaves are used as a euphoriant drug known as marijuana or hashish. Magnification unknown.