Agave leaf. Coloured scanning electron micrograph (SEM) of a section through the leaf of an Agave antillorum plant. The leaf is covered in a layer of wax (pale blue) in which there are stomata, pores through which gas is exchanged between the plant and the atmosphere. Water is stored in the cells (green) below the wax. Among these cells is a sharp crystalline needle, or raphide (purple). Raphides cause pain to any herbivore that eats the leaves of this plant. The evaporation-preventing wax and water-storing cells are adaptations to the arid regions in which the plant grows. Magnification: x95 at 6x6cm size. x150 at 4x5"~SQUARE"