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.
Three species of maple trees are predominantly used to produce maple sugar: the sugar maple (Acer saccharum), the black maple (A. nigrum), and the red maple (A. rubrum), because of the high sugar content (roughly two to five percent) in the sap of these species.