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.
Sugar maple trees average about 1 foot of height growth and 0.2 inch of diameter growth annually for the first 30 to 40 years. Hence a 30-year-old tree might be 6 to 8 inches in diameter and 30 to 35 feet in height. After about 140 to 150 years, height growth ceases and radial growth slows greatly.