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.
Michigan State University Extension provides the following information about maple syrup production in Michigan and how it is a good example of a natural resource enterprise. maple syrup season lasts only four to six weeks in the early spring when maple trees are dormant (i.e. before leaf buds swell and break open). When daily temperatures start to consistently rise above freezing maple sap begins to push up from the roots into the upper portions of the tree.