Marsilea schelpeana Launert
Common names: water clover
Marsilea schelpeana is an aquatic plant with a creeping stem, bearing stalked, floating leaves. It is found in areas that become marshy after rain, but dying down when dry.
Small, aquatic or semi-aquatic plants rooting in mud; the floating form’s leaf stalk can grow up to 140 mm long, longer than the dry land form. Leaflets are roundish, smooth, with entire margins. Seed-enclosing organs, known as sporocarps, are single or crowded, held at an angle of up to 140° (obtuse-angled) to the pedicel, very dark brown. Sporocarps are toothed; the one situated below is inconspicuous or absent, the tooth above is prominent, sharply toothed and slightly curved.
According to the website http://redlist.sanbi.org, Marsilea schelpeana is assessed as Vulnerable (VU), as it is known from only a few locations and experiencing an ongoing decline due to habitat loss in the form of urban expansion and agriculture.
Distribution and habitat
Marsilea schelpeana is endemic to the southern and Eastern Cape, along the coastal plain, at an altitude of ± 200 m. It grows along seasonal pools, dams or watercourses, where it can form the mat-growth habit.
Derivation of name and historical aspects
The genus name Marsilea is named after an Italian naturalist, Count Luigi Fernandino Marsiggli (Marsilius/Marsili), who died in 1730, and the species name schelpeana is named after the late Professor E.A.C.L.E Schelpe from the University of Cape Town Botany Department. There are ± 70 species nearly found all over the world, 18 of which are found in southern Africa.
Marsilea is taxonomically poorly understood. Placing them into a genus is not as difficult as separating to species level; as the species are remarkably look-alike when in vegetative phase. M. schelpeana is similar to M. macrocarpa, but can be distinguished by the sporocarps obtuse angled to the pedicel, its sharply-pointed tooth situated above and by the manner in which the pedicel is attached to the stipe base a few millimetres up from the rhizome. Another aspect to be taken into account when distinguishing the two is their distribution range, M. macrocarpa is widespread from the Eastern Cape to the Democratic Republic of Congo, whereas, M. schelpeana is only restricted to the Eastern and southern Cape.
Marsilea schelpeana is a fern of seasonally dry areas where water is commonly present during the rainy season, or where water level fluctuates from one season to another. Marsileas undergo three different growth stages; the arrival of rains, stimulates germination of spores or dormant subterranean rhizomes produces fronds with 4 characteristic clover-like leaflets, botanically known as pinnae. Then during the period of rapid rhizome growth, leaves are usually flooded and grow into the surface where they float upon the water, since the spores and rhizomes grow in mud; in this stage there is usually no production of spore-cases (sporocarps). As the water moves away in late summer and autumn, the fronds are forced to stand erect, although rhizomes may remain inundated. The third stage is reached once the water has dried up and the plants are left growing on rapidly drying mud or sand. When the rhizome growth slows down, new fronds become smaller, the sporocarps are now produced above the rhizomes in the case of M. schelpeana, the surface dries up, leaves die off, sporocarps matures and the plant goes dormant as to withstand the dry season. Beginnings of rain also help sporocarps to release their spores, probably with the help of parasitic insects that bore holes into the sporocarps to crack the very hard sporocarps walls.
- Crouch, R.N., Klopper, R.R., Burrows, E.J. & Burrows, M.S. 2011. Ferns of southern Africa: a comprehensive guide. Struik, Cepe Town
- Urton, N. & Page, D. 1993. Plants of the Swartkops Valley bushveld. Zwartkops Trust.
Threatened species monitoring programme: CREW
Plant Type: Aquatic
SA Distribution: Eastern Cape
Soil type: Sandy