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.
Overview. Many different species of maple trees (Acer sp.) exist, all of which can be grown from seed. Maple fruits or nuts, also called samaras, ripen and drop to the ground in fall, except for red and silver maples, which mature and drop in late spring or early summer.verview. Many different species of maple trees (Acer sp.) exist, all of which can be grown from seed. Maple fruits or nuts, also called samaras, ripen and drop to the ground in fall, except for red and silver maples, which mature and drop in late spring or early summer.