I remember learning about this plant when I was a Master's Student at Missouri State University. I had collected and pressed this plant as part of some project, and was trying to identify it. It wasn't one of the big three plant families, the ones I could then recognize without looking it up. It isn't an aster, bean, or mint. So I had to key it out from the beginning. There was one key characteristics that really stood out - the plant will turn black-blue upon drying. I was working with freshly gathered specimens at the time, so I had to wait a couple of days for the plants to dry out. Sure enough - the entire plant turned black-blue. I don't have a photo of that process, only live plants blooming on a glade at Ha Ha Tonka above the Devil's Kitchen.
Previously a member of the now Scrophulariaceae (Figwort) family, it is now classified in the Orobanchaceae (Broomrape) family.
Capture July 21, 2022. Ha Ha Tonka State Park