Floating fern

Appearance

S. natans has two nickel-sized leaves lying flat against the surface of the water, and a third submerged leaf which functions as a root. Flotation is made possible by pouches of air within the leaves. Cuticular papillae on the leaves' surface keep water from interfering with the leaves' functioning, and serve to protect them from decay. Spore cases form at the plant's base for reproduction.

The leaves of S. natans block sunlight from reaching very far underwater. This is helpul to many freshwater fish, providing safe hiding places to breed in, but can interrupt the photosynthesis of many underwater plants. S. natans can eventually cover entire ponds or lakes without ecological competition, starving other plant species.

Distribution

S. natans is widely distributed, being native to several continents. In Africa, S. natans is native to Algeria, Egypt, Libya, Morocco, and Tunisia. In Asia, the plant is native to Afghanistan, Azerbaijan, China, Cyprus, India, Indonesia, Iran, Iraq, Israel, Jordan, Kazakhstan, Lebanon, northwest Pakistan, the Russian Federation, Japan, Korea, Saudi Arabia, Syria, Taiwan, Thailand, Turkey, and Uzbekistan. In Europe, it is native to Belarus, Belgium, Bulgaria, the states within the former Czechoslovakia, France, Germany, Hungary, Italy, Moldova, the Netherlands, Poland, Romania, the southern European portion of the Russian Federation, Spain, Ukraine, and the states within the former Yugoslavia.