Today we have pollination speculation. First, I'm going to hypothesize that the dark anthers are an aid to pollination. Somehow the color difference between the brown anthers and the rest of the yellow flower helps the buzzing bees find the right spot. On senna flowers, the bees are there for the pollen, as much or more than for any nectar. Only bees that buzz while hanging on the anthers are rewarded. The pollen must be shaken from the open ends of the anthers. Secondly, I'm hypothesizing that the plants, with their closed tubular anthers, are keeping their powder dry. Notice the shape is similar to the powder horns used for muzzle loading firearms. Wild senna is about two meters tall, with one inch flowers. It grows in prairies and fens in CT(SC), DE, GA, IL, IN, KY, MA(E), MD, ME, MI, NC, NH(E), NJ, NY, OH, PA, RI(X), SC, TN, VA, VT(T), WI, WV, and ON. Ives Fen Preserve, Lenawee Co MI, 7/29/14.