Classification
 Nomenclature
Scientific Name:
Marsilea mutica Mett., Ann. Sci. Nat. Bot. sér. 4, 15: 88 (1861)
Synonymy:
Holotype: lieux inondés à Kanala [flooded ground around Kanala], New Caledonia, E. Vieillard, 1855-1860, P 00636716 (online!)
Etymology:
From the Latin muticus (blunt, without a point), a reference to the shape of the lamina segments.
Vernacular Name(s):
nardoo; smooth nardoo
 Description

Aquatic fern.  Rhizomes submerged, long-creeping, 1–2 mm in diameter, rooting at nodes, straw-coloured, bearing colourless septate hairs up to 2 mm long near the apex.  Leaves solitary at each node, 90–330 mm long, glabrous; stalks 70–300 mm long, each terminating in 4 flabellate segments; segments broadly obovate to flabellate, 10–38 mm long, 9–38 mm wide, green or sometimes streaked brown with false veins between the true veins on the underside; distal margin rounded, entire. Sporocarps solitary, almost globose, each 4–5 mm long, glabrous, on unbranched stalks 3–15 mm long.

 Recognition

Marsilea mutica is a distinctive plant whose creeping rhizomes root on the bottom of ponds or standing water, and produce 4-lobed leaves on long stalks that float on the surface of the water.  In New Zealand the leaves are uniformly green, or with streaks of brown running between the veins, but in Australia they often have horizontal brown markings.  Sporocarps are usually produced as the habitat dries out.

 Distribution

North Island: Auckland, Southern North Island

South Island: Canterbury

Altitudinal range:  5–140 m.

An Australian and New Caledonian species commonly grown in aquaria and garden ponds, and known to have become established temporarily in four North Island localities, the Waitākere Ranges, Hūnua, Pukekohe and Paekakariki, and one South Island locality near Kaiapoi, Canterbury.

 Habitat

Recorded from farm ponds, standing water and swampy ground, sometimes growing with Callitriche stagnalis, Lemna sp., and Azolla rubra, or in Juncus articulatus turf.

 Biostatus
Exotic
 First Record

Brownsey (1988, p. 27).  Voucher: WELT P013485, P020044, 1986.

 Notes

Marsilea mutica is considered potentially poisonous to horses, cattle and sheep in Australia because of the presence of thiaminase (McKenzie 2012).  However, the species is too sporadic to cause any problem in New Zealand.

 Bibliography
Biosecurity New Zealand 2012: Regional Pest Management Strategies Database. http://www.biosecurityperformance.maf.govt.nz/
Brownsey, P.J. 1988: Pteridophyta. In: Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. Flora of New Zealand. Vol. IV. Naturalised Pteridophytes, Gymnosperms, Dicotyledons. Botany Division DSIR, Christchurch.
Brownsey, P.J.; Perrie, L.R. 2015: Marsileaceae. In: Breitwieser, I; Heenan, P.B.; Wilton, A.D. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 8. Manaaki Whenua Press, Lincoln.
McKenzie, R. 2012: Australia's poisonous plants, fungi and cyanobacteria. CSIRO Publishing, Collingwood, Victoria.
Mettenius, G.H. 1861: Filices Novae Caledoniae a Cl. Viellard collectae. Annales des Sciences Naturelles; Botanique sér. 4, 15: 55–91.