Light micrograph of the epidermis of a tulip leaf. The upper cell layer, the epidermis, can be peeled off quite well in the garden tulip. Only the reinforced cell walls of the sphincter cells light up in polarised light with the typical cross in complementary colours. The less strengthened cell walls of the remaining epidermal cells light up only faintly. Microscopic contrast method : Polarisation contrast. Magnification 400x at a print width of 10 cm.