There is an annual prairie plant that grows here in Iowa, and it is called partridge pea, Cassia fasciculata. The plant has little glands at the base of its leaves. Those glands are called extrafloral nectaries. The plant releases sugary fluids that attract ants and other insects.
The prevailing notion is that the nectaries attract ants, which attack any insect present on the stems and leaves, presumably removing insects that would eat the plant.
Do they attract ants? Well, I think so. Here are some acrobat ants, probably Crematogaster species.