Salvinia is a genus (10 species) of small floating, aquatics ferns. From each node, leaves (2) spread horizontally or nearly so on the surface of the water. The exposed side of a floating leaf is actually the lower (adaxial) surface, i.e., the leaf is twisted from its normal position. On the surface of the floating leaf are numerous hairs, each with finger-like branches at the tip, and these hairs are very effective in keeping the leaf surface dry (nonwettable) by trapping air, thereby permitting the plant to remain floating and to prevent the stomates from being covered with water. Salvinia, called water spangle or floating fern, has no true roots on the adult plant, but instead has a finely dissected submerged leaf type that appears rootlike.
Species of Salvinia are greatly feared as weeds in freshwater, where they can rapidly multiple and totally cover a quiet body of water and thereby make boating very difficult and greatly harming the natural food chain of ponds and lakes. Aggressive sanitation is used to eliminate this weed when it is observed.
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