Salvinia-Click for more info

Free floating, rootless aquatic fern. Horizontal, branching rhizomes float just below the water surface and produce, at each node, two floating to emergent leaves, and a third, submersed leaf that is dissected into filaments. Floating leaves are orbicular to oval in shape, with heart shaped bases and rounded to notched tips. Leaf length ranges from 0.4 to 2.0 cm. Smaller, orbicular leaves lie flat on the water surface; larger leaves become elongated and fold upright on the midrib. Shade grown leaves remain broadly orbicular, and emerald green. Leaves grown in full sun become larger and elongated and often change from emerald green to rusty brown with maturity and senescence. The upper surfaces of floating leaves are uniformly covered with rows of white, bristly hairs. The stalks of each hair divide into four thin branches that are spreading and free at the tips. The branching hairs create a water repellent shield. Long chestnut colored hair coats the underside of floating leaves, the submersed filaments, buds and the rhizome.  USGS