Salvinia, a genus in the family Salviniaceae, is a floating fern named in honor of Anton Maria Salvini, a 17th-century Italian scientist. Watermoss is a common name for Salvinia. The genus was published in 1754 by Jean-François Séguier, in his description of the plants found round Verona, Plantae Veronenses There are currently twelve species recognized, at least three of which (S. molesta, S. herzogii, and S. minima) are believed to be hybrids, in part because their sporangia are found to be empty.
Salvinia is related to the other water ferns, including the mosquito fern Azolla. Recent sources include both Azolla and Salvinia in Salviniaceae, although each genus was formerly given its own family.
Salvinia, like the other ferns in order Salviniales are heterosporous, producing spores of differing sizes. However, leaf development in Salvinia is unique. The upper side of the floating leaf, which appears to face the stem axis, is morphologically abaxial.
From a human point of view, when their growth is robust the plants pose a particular hindrance on certain lakes, having choked off much of the water in Lake Bistineau near Doyline in Webster Parish, Louisiana. Other problems have persisted in a second Webster Parish site, Caney Lakes Recreation Area.
Small, floating aquatics with creeping stems, branched, bearing hairs on the leaf surface papillae but no true roots. Leaves are in trimerous whorls, with two leaves green, sessile or short-petioled, flat, entire, and floating, and one leaf finely dissected, petiolate, rootlike, and pendent. Submerged leaves bearing sori that are surrounded by basifixed membranous indusia (sporocarps); sporocarps of two types, bearing either megasporangia that are few in number (approximately 10), each with single megaspore, or many microsporangia, each with 64 microspores. Spores of two kinds and sizes, both globose, trilete. Megagametophytes and microgametophytes protruding through sporangium wall; megagametophytes floating on water surface with archegonia directed downward; microgametophytes remaining fixed to sporangium wall. The small, hairlike growths, known as microgametical follicles, are not known to have any productive function, and are currently a biological mystery.
Giant salvinia (Salvinia molesta) is a commonly introduced invasive weed in warm climates. It grows rapidly and forms dense mats over still waters. It is native to South America. A tiny weevil, Cyrtobagous salviniae, has been used successfully to control giant salvinia.
The salvinia effect describes the stabilization of an air layer upon a submerged hydrophobic (water repellent) surface by hydrophilic (water loving) pins. This physic-chemical phenomenon was discovered on the floating fern Salvinia molesta by the botanist Wilhelm Barthlott (Universität Bonn) while working on the Lotus effect and was described in cooperation with the physicist Thomas Schimmel (Karlsruher Institut für Technologie), fluid mechanist Alfred Leder (Universität Rostock) and their colleagues in 2010.