Anatomy of a eudicot leaf

(1) The upper leaf surface is epidermis with a secreted layer of cuticle.

(2) The lower leaf surface is also covered with cuticle. Gas exchanges between air inside and outside of the leaf occur  at stomata positioned mainly in the lower leaf epidermis.

(3) The bulk of the leaf is mesophyll, a type of photosynthetic parenchyma. In many leaves, mesophyll occurs in two distinct forms: elongated palisade mesophyll attached to the upper epidermis, with (4) spongy mesophyll below it.

(5) Vascular bundles of xylem (blue) and phloem (pink) form the leaf’s veins.