These flowers in the Asclepiadaceae (milkweed) family have evolved to look, feel, and smell exactly like a decomposing mammal. Their red/yellow colors mimic rotting and decomposing flesh and fat, they have a soft and pulpy surface and absolutely reek. Some of them even fool flies and make them lay their eggs on their flowers so pollination can occur!
Fun fact: We actually had a few carrion flowers make an appearance during the first week of the Monet’s Garden display in the Enid A. Haupt Conservatory. They were a bit of an Easter egg, as they were hidden away behind some of the more colorful spring blooms, but even if you didn’t see them, you caught a pungent whiff within four or five feet.
Our horticulturists felt they were the kind of florescence Monet’s daring side would have appreciated. I tend to agree. —MN
Edit: As I know I’ll get comments about this, let me confirm for the sake of completeness that Asclepiadaceae is now, to the best of my knowledge, considered a subset under the Apocynaceae family. Lo, but botany is a complicated business at times.