The morphology and anatomy of a leaf can allow you to predict the conditions that the plant is adapted to. In particular, what is the water availability in that plant's environment?
A leaf in "normal" conditions is called mesophytic (meso- means middle), meaning it is not particularly adapted for either high or low water conditions.
Hydrophytes (literally "water plants") are adapted to living in aquatic conditions.
Below is an image of another hydrophytic leaf. This one is from a monocot, Potamogeton. Note the similarity to the Nymphaea leaf and the distinct differentiation between regions of mesophyll. A good example of convergent evolution to similar environmental pressures!
Location of Stomata
Because Nymphaea is aquatic and sits on top of the water, the stomata are located only in the upper epidermis. You can locate them in the cross section by finding the gaps (stomatal pits) in the palisade mesophyll. Why wouldn't there be stomata in the lower epidermis?
If you see strange branching structures within your Nymphaea leaf cross section, you may be looking at an astrosclereid (astro- meaning star). This is a branching sclerenchyma cell with a thick secondary wall. What function might these cells have?
Xerophytes (literally "dry plants") are adapted to living in dry conditions with low water availability.
The image below shows the cuticle of the Nerium leaf. Notice how thick it is on the upper (adaxial) surface of the leaf and how it changes in thickness as it transitions to the lower (abaxial) surface.
Location of Stomata
In xerophytic leaves, stomata tend to be located on the lower (abaxial) surface. This side of the leaf is usually cooler, as the upper (adaxial) surface is facing the sun. In extremely dry conditions, stomata might be further protected from the desiccating outer air by being located in stomatal crypts.
Gymnosperms: The Original Xerophytes
Though pines are not angiosperms, they have xerophytic leaves (needles). Note the features this pine needle has in common with the Nerium leaf.