Salvinia

Salvinia, the sole genus in the family Salviniaceae, is a floating fern. The Salviniaceae are related to other water ferns, such as the mosquito fern. Recent sources include both Azolla and Salvinia in Salviniaceae, although each genus was formerly given its own family. Salviniaceae and the other fern families in the order Salviniales are heterosporous, producing spores of differing sizes.




 * Salvinia auriculata
 * Salvinia biloba
 * Salvinia cucullata
 * Salvinia cyathiformis
 * Salvinia hastata
 * Salvinia herzogii
 * Salvinia minima
 * Salvinia molesta
 * Salvinia natans
 * Salvinia nymphellula
 * Salvinia oblongifolia
 * Salvinia radula
 * Salvinia rotundifolia
 * Salvinia sprucei

Leaf development in Salvinia is unique. The upper side of the floating leaf, which appears to face the stem axis, is morphologically abaxial.

About ten species

Distribution
Mostly tropical, North America, Mexico, West Indies, Central America, South America, Eurasia, Africa including Madagascar.

Description
Small, floating aquatics with creeping stems, branched, bearing hairs but no true roots. Leaves in whorls of 3, with 2 leaves green, sessile or short-petioled, flat, entire, and floating, 1 leaf finely dissected, petiolate, rootlike, and pendent. Submerged leaves bearing sori that are surrounded by basifixed membranous indusia (sporocarps); sporocarps of 2 types, bearing either megasporangia that are few in number (ca. 10), each with single megaspore, or many microsporangia, each with 64 microspores. Spores of 2 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.

Economic Uses
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.

S. natans is commonly used in aquariums as a decorative floating plant.