Elodea

Elodea canadensis, or Anacharis Alsinastrum, the American water-weed, a submerged aquatic plant belonging to the order Hydrocharidaceee. Its long, much-branched stems are very brittle, and, as they root freely at the nodes, the plant, broken up by water- birds, has spread rapidly, though, as it is dioecious, it does not seed in England. Its whorled, linear-oblong leaves clearly exhibit the rotation of the protoplasm in their cells. Introduced from America into Ireland about 1836, and into England about 1841, it spread rapidly throughout our rivers, canals, and ponds, and has since proved a great hindrance to mills and to navigation.