Monographs Details: Salvinia
Authority: Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.
Description:Genus Description - Plants floating on water; rhizome slender, hairy, horizontal, nodes distant, roots distant; leaves whorled, dimorphic, two at each whorl round to elliptic, flat to folded upward by the midvein, a third pendent, finely dissected to veins, trailing, acting as a root; vegetative leaves oblong or orbicular, herbaceous, with distinct midvein, hairs on top surface in groups of four with fused bases, the tips free or fused at the very tips forming a cage-like structure, hairs on undersurface septate; veins netted; heterosporous, the sporangia on the trailing dissected leaf in stalked, subglobose sori (spo-rocarps), covered with thin-walled, hairy indusium, megasporangia and microsporangia on same plant but in different sporocarps; spores tetrahedral.
Discussion:Type: Uncertain, usually said to be Salvinia natans (Linnaeus) Allione [=Marsilea natans Linnaeus].
Salvinia is a pantropical genus of about 11 species with seven species in America. They are plants of ponds and slow-moving rivers.
The genus was monographed by Herzog (1935), and the Salvinia auriculata complex was worked on by de la Sota (1976), Mitchell (1972), and Mitchell and Thomas (1972). Salvinia can be a noxious weed, S. molesta Mitchell (1972) being the most aggressive, as evidenced by its rampant growth on the artificial Lake Kariba in Zambia and Rhodesia (Zimbabwe) (Mitchell, 1969). This species, demonstrating hybrid vigor and abortive spores, is postulated by Mitchell (1972) to possibly be a hybrid of horticultural origin in South America which has now spread to Africa, Ceylon, Indonesia and Australia.
Salvinia is related to Azolla but together they go back many millions of years with no distinct ties to the other ferns. Azolla and Salvinia are placed together in one order, sometimes in a single family. Salvinia is distinct by its floating habit, orbicular to oblong vegetative leaves with compound hairs, and rootlike leaves with sporocarps.
References: de la Sota, E. R. 1976. Sinopsis de las especies argentinas del género Salvinia. Bol. Soc. Argent. Bot. 17: 47-50; Herzog, R. 1935. Ein Beitrag zur Systematik der Gattung Salvinia. Hedwigia 74: 257284; Mitchell, D. S. 1969. The ecology of vascular hydrophytes on Lake Kariba. Hydrobiologia 34: 448464; Mitchell, D. S. 1972. The Kariba weed: Salvinia molesta. Brit. Fern Gaz. 10: 251-252; Mitchell, D. S. & P. A. Thomas. 1972. Ecology of waterweeds in the neotropics, an ecological survey of the aquatic weeds Eichhornia crassipes and Salvinia spp. and their natural enemies in the neotropics. UNESCO Techn. Pap. Hydrol. 12: 1-50; Weatherby, C. A. 1937. A further note on Salvinia. Amer. Fern J. 27: 98-102.