Milkweed Reproduction

Day 272: The first phase of this project consisted of learning to identify the reproductive structures of Asclepias syriaca, Common Milkweed. You'd think that milkweeds kept the family jewels in the same place as other plants do, but as it turns out, the flower is rather different in that it centers on a gynostegium (new word for me!), which is comprised of fused stigmas and stamens. What lay people would call the "flower" (the white part, in this case) is the corona. It consists of hoods and horns (five each). The petals of the flower depend beneath it. Between hoods, a careful observer will note a swollen brownish bump at the inner end of the stigmatic slit (see center image). This is the corpusculum. It is essentially the "bear trap" in which an insect's leg can become ensnared. Attached to the corpusculum are two pollinia, sticky agglomerations of pollen. In the instance of A. syriaca (or at least those in my garden), the corpusculum and attached pollinia measured something in the neighbourhood of half a millimeter long. I was able to tease two "units" out using the microscope and a dissecting needle, but once on the tray, I could barely see them with my naked eye. Nevertheless, "sticky" was the operative word. They gummed themselves to the tip of the dissecting needle nicely, and I was able to transport them to the garden. As to whether or not I successfully poked them into the stigmatic slit of a second plant remains to be seen. I had no way to magnify the flower while keeping both hands free to perform the cross-pollination. There was an unexpected bonus to this experiment: I discovered that milkweed is deliciously fragrant as I stood there with my beak in the blossom, pretending I was a bug.