About Lemna gibba L.
Lemna gibba L., commonly called gibbous duckweed, swollen duckweed, or fat duckweed, is a species of duckweed in the genus Lemna. This species has a simple floating plant body called a thallus that sits on the water surface, with a diameter between 3 and 5 mm (0.12 to 0.20 inches). A single root hangs down from the thallus into the water. It is a common duckweed that grows in a wide variety of still or slow-flowing water bodies, and can also grow on mud or damp rocks. This duckweed is distributed across temperate regions, ranging from Europe (including Britain) to the Himalayas, Africa, South America, and North America. It is one of the most common small water plants in Britain, where it forms recognizable green mats that cover stagnant water bodies. It is widespread across most of Great Britain, but absent from much of Scotland and Shetland. In Ireland, it occurs mainly in the north and east of the island. Overall, the species has a very broad global distribution, and is only absent from polar areas and the tropics. Distribution records for this species are available via the Charms of Duckweed (archived 2012-08-19 at the Wayback Machine) for worldwide coverage, and the National Biodiversity Network Gateway for Britain only. This species mostly spreads via vegetative reproduction, though flowers are occasionally produced in shallow water that receives full sun. When it grows to cover the entire surface of a pond, it can make the water look solid. In parts of north-west England, this full covering of duckweed was tied to the myth of Jenny Green-teeth, a pond elf or monster said to lure children into ponds and drown them; the duckweed was used to indicate her presence, to scare children away from these ponds.
