Leaf oil glands. Coloured scanning electron micrograph (SEM) of a thyme plant's leaf surface (Thymus vulgaris). Two types of leaf trichomes (hairs) are seen. The small spiky, hairs may have a protective function or reduce evaporation from the leaf. The flattened structures (pink) are modified glandular hairs that are the source of the aromatic oil of thyme. Thyme is used as a herb in cooking. It also has medicinal properties. Magnification: x320 when printed 10cm high.