The water milfoil family occur most often in the southern hemisphere.  The species found in Alaska and the northern hemisphere are aquatic plants.  The leaves are deeply divided into thread-like segments.  Male flowers have 3-4 sepals, 4 petals, 2-8 stamens and are found near the top of the plant.  Female flowers are found near the bottom of the flower cluster.  The sepals and petals fall off when the flower opens.