Thalia dealbata, or powdery thalia, is a fascinating plant that I was introduced to this past August while on a botany trip with Pete Kozich and Stephen Dilks. A member of the mostly tropical arrowroot family (Marantaceae), T. dealbata is the only member of this family to be found in Missouri and only in the low and wet areas of the southeastern portion of the state. We found these plants a little late in their flowering season but with a few blooms in prime condition remaining at Otter Slough Conservation Area.
The leaves of Thalia are what the plants are primarily known for, looking very reminiscent of the cannas and very tropical in appearance. However, doing a little research after seeing these guys for the first time, I have become fascinated with the flowers and the pollination mechanism they developed. First of all, what appears to be a single flower in the image posted here is actually a pair of blooms in mirror image of each other. Additionally, the gorgeous purple petals are not petals at all but highly modified and sterile stamens (staminodes). This is just the beginning of the weird story of these flowers. These staminodes are key to a pollination strategy that literally throws pollen in the face of and often ends in the demise of all but the strongest of would-be insect pollinators. I was going to attempt to try and describe the pollination biology of this system, but this has been expertly described by Price and Rogers in a 1987 article published in Missouriensis. I highly recommend you give this a read!
A Thousand Acres of Silphiums 
Beautifully captured, Bill. Great write up.