Mesophyll

Mesophyll (from the Greek mesos, "middle;" phullon, "aleaf") is the cellular tissue in the interior of the leaf (q.v.). In the ordinary horizontal leaves of flowering plants it is usually divided into two parts - (1) the palisade tissue, one or two layers of closely-packed, vertical, prismatic cells, rich in chlorophyll, and acting as the assimilatiny tissue, just below the upper epidermis; and (2) the spongy mesophyll, loosely-arranged cells, sometimes stellate, with large intercellular spaces communicating with the stomata (q.v.) in the lower epidermis. This paler-coloured tissue is traversed by the veins of the leaf and acts mainly as the transpiring tissue.