I noticed a cool feature of the bleeding heart flower. As it matures, each blossom undergoes a two-stage opening of its interestingly shaped petals.
The young blossom, shown upper left, doesn’t have any openings to either its pistil (the pollen-receiving structure) nor the anther (the pollen-producing structure).
Upper right shows a middle-aged blossom which has unfurled the first set of petals. This provides an opening that an insect could enter the flower to gain access to the pistils (containd inside the “heart” of the flower).
As the flower ages futher, another set of petals open, revealing the anthers (lower left). At lower right is another shot of the same blossom, taken from the side to illustrate the exposed anthers.
I theorize that this approach gives the bleeding heart plant an evolutionary reproductive advantage. By exposing each part of the flower in series, it encourages cross-plant pollination. An insect visiting a young blossom may carry pollen from another plant, but can’t pick up pollen from the self-same blossom. This grants an advantage to the offspring, which will have a more genetic variation, and will therefore be more likely to weather future selective pressures. Should this plant be out of range of any other individuals, self pollination is still possible (either from one older blossom to a younger one) or via one older blossom to itself.
Given this morphology I’d further hypothesize that the blossom might have two sources of nectar (one in each compartment) to encourage pollinators to visit both the anthers and the pistils.
Update: I was feeling guilty, as I hadn’t actually dissected a flower when I wrote the above text. I wasn’t really sure where the pistil was. Well, I think that it is right next to the anthers (in the “drop”), not inside the “heart” of the flower as I’d speculated — at least in a mature flower. So my hypothesis may be invalid, or only partially correct (if, for example, the pistil elongates as the flower matures. It is rather a puzzle… why would the flower partially open, but keep the anther and pistil under wraps? I may have to do more investigation.)