Marsilea quadrifolia L., Marsileaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: European pepperwort, European waterclover

French: fougere d'eau

Japanese: denjiso

Spanish: aigret, viola

Habit:  aquatic fern

Description:  "Plants forming diffuse colonies.  Rhizome 0.5-1.3 mm thick, reddish brown to black, sparsely hairy to glabrate, bearing short nodal shoots, nodal and internodal roots 0.2-0.3 mm thick, internodes 0.6-5 cm long; rhizome in water 0.9-2.0 mm thick, green, glabrous, aerenchymatous, internodes 4-12 cm long.  Land leaves with terete petioles 5.4-16.5 cm long, 0.5-1.0 mm tick, leaflets 0.7-2.1 cm long, 0.6-1.9 cm wide, symmetrical, flabellate, glabrous or with a few non-overlapping hairs; floating leaves with terete petioles 14-30 cm long, 1.0-1.5 mm thick, leaflets 1.3-3 cm long, 1.2-3.1 cm wide; hydropoten irregularly distributed or absent.  Fertile leaves produced on land (rarely in water) on long shoots or short shoots, bearing 1-3 sporocarps on a branched or unbranched peduncle attached 1-12 mm above petiole base; unbranched peduncle or ultimate branches of peduncle 3-16 mm  long, common trunk of branched peduncle or ultimate branches of peduncle 3-16 mm long, common trunk of branched peduncle 1-4 mm long (rarely 2-3 unbranched peduncles attached separately to the same petiole).  Sporocarps 4.0-5.6 mm long, 3.1-4.0 mm wide, 2.3-2.8 mm thick, rounded, oval, or elliptical in lateral view, elliptical to nearly round in cross section, dark brown to black, hairy but soon glabrate; raphe 1.4-1.9 mm long, inferior tooth usually absent, superior tooth absent or 0.1-0.2 mm long, acute; sporocarp veins ca 20, forking halfway from median vein, the branches anastomosing just before the tips or free.  Sori 10-17 per sporocarp, borne on a sorophore with a free, acute tip, ca 12 microsporangia and 3-7 megasporangia per sorus; microspores ca 43 per sporangium, 56-61 μm in diameter; megaspores 560-610 μm long, 355 μm wide, with an apical papilla 60  long" (Johnson, 1986; pp. 35-39).

Habitat/ecology:  "A major weed of paddy fields and a troublemaker in ponds, lakes and irrigation systems.  It frequents paddy crops and warm, shallow, muddy edges of fresh water ponds" (Holm et al., 1997; pp. 455, 457).

In North America, "found in ponds, river backwaters, and marshes, where it occurs from the shores out to a depth of ca 0.5 m" (Johnson, 1986; pp. 35-39).

Propagation:  Spores and possibly by birds or dispersal by flowing water (Johnson, 1986; pp. 35-39). "Vegetatively by means of creeping rhizomes or following dispersal and establishment of rhizome fragments" (Holm et al., 1997; p. 458).

Native range:  Europe; also cultivated and naturalized elsewhere (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Philippines Philippine Islands	Philippine Islands	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Queensland		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
Cambodia Cambodia	Cambodia (Kingdom of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)
China China	China (People's Republic of)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
Indonesia Indonesia	Indonesia (Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)
Japan Japan	Japan		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
South Korea South Korea	South Korea (Republic of)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
Malaysia Malaysia	Malaysia (country of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)
Mexico Mexico	Mexico (United Mexican States)		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
South America (Pacific rim) South America (Pacific rim)	Colombia		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
Taiwan Taiwan Island	Taiwan Island		Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 455)
Thailand Thailand	Thailand (Kingdom of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)
Vietnam Vietnam	Vietnam (Socialist Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 67, 78)

Control:  If you know of control methods for Marsilea quadrifolia, please let us know.