Leaf of Helianthus:
In between the two epidermal layers is the mesophyll. It is differentiated and has well developed palisade tissue below the upper epidermis. Above the lower epidermis and below the palisade tissue is the spongy parenchyma which has loosely arranged cells with large number of air chambers. Palisade tissue is chlorophyllous and it is the chief photosyn- thetic tissue of the plant. There are a few chloroplasts in the spongy parenchyma cells also but their main function is storage. These are rich in starch grains.
Leaf of Maize:
It is undifferentiated. But the mesophyll cells below the upper epidermis may show a compact arrangement.