Marsilea minuta L., Marsileaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: clover fern, dwarf waterclover, pepperwort, small water clover, water clover

Habit:  aquatic fern

Description:  "Plants forming extensive but diffuse colonies.  Rhizome 0.4-0.8 mm thick, green to light brown, densely covered with tan hairs at apices but glabrate proximally, sometimes bearing short branches with numerous leaves at nodes, nodal and internodal roots 0.1-0.3 mm thick, internodes 1-3.5 cm long; rhizome in water 0.5-0.8 mm tick, green to brown, glabrous, internodes 4-11 cm long.  Land leaves with erect terete petioles 5-13 cm long, 0.4-0.8 mm thick, leaflets 1.2-2 cm long, 0.8-1.7 cm wide, cuneate to flabellate, glabrous to sparsely hairy, with concave, straight, or convex lateral margins and entire to crenulate terminal margins; leaves in water often with leaflets emergent rather than floating, with stiff terete petioles 13.5-47 cm long, 0.3-0.8 mm thick, leaflets 1.7-1.8 cm long, 1.5-1.6 cm wide; hydropoten infrequent.  Fertile leaves produced on land, bearing 1-4 sporocarps per leaf, on either branched or unbranched peduncles attached at or slightly above the base of the petiole, unbranched peduncles and ultimate divisions of branching peduncles 2.6-6.0 mm long, the common trunk of branched peduncles 0.4 mm long.  Sporocarps 2.6-4.1 mm long, 2.4-3.1 mm wide, 1.3-1.7 mm thick, nearly round to slightly oblong in lateral view, ovate or elliptical in cross section, brown to black, hairy to glabrate; raphe 1.5-2.2 mm long, inferior tooth 0.3-0.6 mm long, obtuse or truncate, or absent, superior tooth 0.3-0.6 mm long, acute; sporocarp veins ca 15, forking midway, branches often anastomosing at tips.  Sori 9-12 per sporocarp, attached to a sorophore with a free acute tip, 9-14 microsporangia and 2-7 megasporangia per sorus.  Microspores 50-64 per sporangium, 50-75 μm in diameter, with 1-2 spores per sporangium occasionally brown, misshapen, up to 32 μm long.  Megaspores 400-525 μm long, 355-380 μm wide, with an apical lpapilla 40-65 μm long" (Johnson, 1986; pp. 39-40).

Habitat/ecology:  Low elevations near the coast in fresh water or occasionally in brackish water on sandy or clay substrates. In northeastern Brazil the plants have been collected in seasonal ponds (Johnson, 1986; pp. 39-40).

Propagation:  Spores or rhizomes (Waterhouse, 1994; p. 114).

Native range:  Africa and India. It is found in Trinidad, Tobago and northeastern Brazil, but these may be recent introductions (Johnson, 1986; pp. 39-40).  Australia and New Caledonia (Staples & Herbst, 2005; p. 39).

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		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
Cambodia Cambodia	Cambodia (Kingdom of)		Waterhouse, D. F. (1993) (pp. 67, 78)
Indonesia Indonesia	Indonesia (Republic of)		Waterhouse, D. F. (1993) (pp. 67, 78)
Malaysia Malaysia	Malaysia (country of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Thailand Thailand	Thailand (Kingdom of)		Waterhouse, D. F. (1993) (pp. 67, 78)
Vietnam Vietnam	Vietnam (Socialist Republic of)		Waterhouse, D. F. (1993) (pp. 67, 78)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Comoros Comoro Islands	Comoro Islands	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Control: 

Biological:  Waterhouse (1994, pp. 115-116) lists natural enemies of the species.

Additional information:
Additional online information about Marsilea minuta is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Marsilea minuta as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Marsilea minuta may be available from the Germplasm Resources Information Network (GRIN).

References:

Johnson, David M. 1986. Systematics of the New World species of Marsilea (Marsileaceae). Syst. Bot. Monogr. 11.

Staples, George W./Herbst, Derral R. 2005. A tropical garden flora: plants cultivated in the Hawaiian Islands and other tropical places. Bishop Museum Press, Honolulu. 908 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Waterhouse, D. F. 1993. The major arthropod pests and weeds of agriculture in Southeast Asia. The Australian Centre for International Agricultural Research, Canberra. 141 pp.

Waterhouse, D. F. 1994. Biological control of weeds: Southeast Asian prospects. Australian Centre for International Agricultural Research, Canberra. 302 pp.