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.
Future generations of sugar maples are dependent on seed produced by todayâs mature trees. Trees as young as 22 years can produce some seed but the better crops are produced by much older trees â and sugar maple can live for 400 years. In a heavy seed year millions of sugar maple seed can fall in one hectare of forest.