Progesterone. Print | Email article to a friend | Last updated: January 14, 2015. Progesterone is a hormone released by the corpus luteum in the ovary. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. It may also be involved in the growth of certain cancers.
Maple helicopters fall before the leaves drop from the trees. Maple trees (Acer spp.) produce winged seeds called double samaras, which twirl to the ground in late summer or early fall. They resemble helicopters in motion, earning them the common name of helicopters or whirligigs.
Maples are rightly recognized as the best shade tree for fall color, but Nuttall oak is no slouch. Its deeply lobed leaves turn bright red in mid- to late fall, usually after the maples have dropped. I took these photos last week at Aldridge Botanical Gardens in Hoover, Alabama.