Inga is a genus of trees that are quite common in the neotropics. Two of the species I worked with last summer were Inga (thibaudiana and pezizifera) so I’ve gotten fairly good at identifying the genus.
I find Inga really interesting because of its extrafloral nectaries. “Extrafloral nectaries” may sound really complicated, but actually they’re fairly simple: “extra-floral” meaning not on flowers, and “nectaries” meaning something that provides nectar. With inga, the nectaries are on the leaves, and they attract ants that help protect the tree from herbivory and vines.
Another interesting thing about inga is that it has compound leaves. This means that all the parts that look like leaves are actually leaflets, and the leaves themselves are made up of four to twenty leaflets. Inga leaflets always come in pairs. Inga leaves (and leaflets) can be fairly small, or really big.
Lastly, some Inga can have a winged rachis. The rachis is the part of the leaf that connects all the leaflets together, and when it has a lot of leaf-tissue on it, it’s considered winged. I don’t know if this serves any biological purpose, but it makes them look really cool.