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 trees are probably the easiest tree to recognize because of their distinctive shaped leaves and vibrant colors in the fall. Their seeds are often referred to as helicopters because of their shape and the way they float to the ground. Maple trees are classified as shade trees because of their size. Silver Maples are the fastest growing type of maple tree with a mature spread of 35' to 50'.