Within a plant leaf, most photosynthesis occurs in cells called cells, which are often interspersed with air spaces to maximize gas exchange.

The spongy mesophyll is the kind of cell described.

Explanation:

"Most of the interior of the leaf between the upper and lower layers of epidermis is a parenchyma(ground tissue) or chlorenchyma tissue called the mesophyll (Greek for "middle leaf"). This assimilation tissue is the primary location of photosynthesis in the plant."

The main layers of the leaf are the cuticle, which is the "skin," the palisade mesophyll (the second topmost layer of cells), the spongy mesophyll, which is lower, and the lower cuticle. The spongy mesophyll is so called because it consists of leaf cells interspersed with air, which maximises their access to oxygen.