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.
Maple syrup starts as the sap of maple trees; boiling after harvest concentrates the sweetness and thickens it to the syrupy consistency. Tapping takes place by hand during a few months in the spring, and the labor-intensive process partly accounts for the high price of maple syrup.