Reading a leaf section

A student measured the layers of a leaf in a vertical section and counted the stomata on both faces of three leaves. You will total the layers, find the share of mesophyll, name the kind of leaf, and draw a bar chart.

The idea. The layers are in a dictionary, in micrometres. The three leaves are tuples: the name, the stomata on the upper face, the stomata on the lower face, and whether the mesophyll is divided into palisade and spongy parts.

Your tasks.

1. Set total to the thickness of the leaf, the sum of all the layers.
2. Set mesophyll_share to the percentage of the thickness that is palisade and spongy parenchyma together.
3. In leaf_kind, return "dorsiventral" if the mesophyll is divided, and "isobilateral" if it is not.
4. Set dorsiventral_names to a list of the names of the dorsiventral leaves, in the order of leaves.