Genus Azolla is a type of aquatic fern that has several other synonyms. These synonyms include mosquito fern, fairy moss, and water velvet. The genus Azolla belongs to the family of Salviniaceae, which in turn belongs to the order Salviniales. It is a small fern species that grows in ponds, rivers, and other freshwater bodies. The fern is an important source of nitrogen, which it fixes from the atmosphere into the water where it grows. It is also frequently used as a natural fertilizer in agriculture. Regardless of what you call it, the genus Azolla is a fascinating and important part of the natural world.