Pistia

Pistia stratiotes in the garden pond

The water lettuce ( Pistia stratiotes ), also called green water rose flower or shell, is the only species of the genus within the family of Araceae Pistia ( Araceae ). This floating plant is found worldwide in tropical and subtropical zones in freshwater. It is used as an ornamental plant.

Description

The water lettuce is a aquatic living, stemless, perennial herbaceous plant. It forms a plurality of long roots. The alternate and spirally arranged in a rosette leaves are sessile. The pale - green, spongy, densely covered with fine, consisting of a few cells trichomes leaf blade is broadly obovate with a wide rounded top end and ausgebuchtetem edge with a length of 4 to 5 centimeters.

The inflorescences are very short Blütenstandsschäften. The bracts are leaves- leaf-like, whitish, glabrous on the inside, on the outside tomentose. The flowers are getrenntgeschlechtig, the inflorescence is found only one gender of the flowers. Female inflorescences contain only one flower, they have a single, unilocular, ovoid ovary with a variety of closely related ovules (perpendicular ) are arranged in four to six rows orthotroph. The style is short and is terminal, the scar is numb - brush-like. Male inflorescences consist of two to eight flowers. These each have two stamens, which are only slightly fused together, the anthers open with two vertical slots.

The small, ovoid berry contains few to many seeds. The fruit jumps to irregular and so the seeds are free. The seeds are cylindrical in shape, slightly cut off at the top and in the middle they are eroded.

The wettability of the sheet surface is small. Water trickles into droplets on how it can be also observed in lotus flowers, and does, on the surface of particles of dirt with (lotus effect).

Occurrence

The water lettuce is found in the tropics and subtropics of the Old and New World, in America extends its range to the north into southern Texas and Florida. It is a very ancient, genetically isolated evolutionary lineage.

The water lettuce is mostly in stagnant fresh water, usually found at the edge of lakes and ponds. Mostly it is found at altitudes of up to 1200 meters, occasionally it is also found at higher altitudes.