Light micrograph of a sessile secretory gland on the herb sweet marjoram, Origanum majorana. There are two basic types of secretory glands (or trichomes); stalked and unstalked (or sessile). A number of variations of structure exist but generally between 4 and 12 specialised cells form a small cushion over which a membrane develops. Each cell produces and secretes a cocktail of oils which accumulate beneath the membrane causing it to swell. Plants usually secrete extrafloral substances as a defence against bacteria, fungi or predators. Floral secretions attract insects for pollination purposes. Magnification: x400 at 35mm size.