Fig. 3.3-2. Transverse section of leaf of ivy (Hedera). Like leaves of most species, this ivy leaf consists of almost pure parenchyma, except for its veins. Even though ivy leaves are somewhat tough and leathery, their upper and lower epidermis and all the photosynthetic tissues are composed of parenchyma cells. We can consider the parenchyma to be structural because it makes up most of the bulk of the leaf, but the photosynthetic cells are simultaneously synthetic parenchyma, and the epidermis cells are boundary parenchyma. Notice that the lower half of the leaf has much larger intercellular spaces – is more aerenchymatic – than the upper half. This slide is unusual in that nuclei are stained green rather than the more typical red, although both colors are artificial – unstained nuclei are colorless.