Salvinia
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| Salvinia (Salviniaceae) | ||||||||||||
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 Salvinia natans
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Salvinia, the sole genus in the family Salviniaceae, is a floating fern. The Salviniaceae are related to the other water ferns, including the Mosquito fern, Azolla. Some sources include Azolla in Salviniaceae, although the genus is generally given its own family, Azollaceae.
Described by Séguier, in Pl. Veron. 3: 52. 1754.
Salviniaceae and the other fern families in order Salviniales are heterosporous, producing spores of differing sizes.
Leaf development in Salvinia is unique. The upper side of the floating leaf, which appears to face the stem axis, is morphologically abaxial (J. G. Croxdale 1978, 1979, 1981).
About ten species
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[edit] Distribution
Mostly tropical, North America, Mexico, West Indies, Central America, South America, Eurasia, Africa including Madagascar.
[edit] 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.
[edit] 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.[1]
