Water Lettuce

Pistia (Peony floating weeds, scientific name:Pistia stratiotes L.) is a tropical aquatic plants of the family araceae native to Africa and South America. 1 genus, one species and not something similar with unique plants. As the invasive alien species issue. Has a rosette of pale green, like lettuce leaves.
Extend the roots beneath the strain. Flowers bloom from between the leaves. Spadix surrounded by small spathe light green florets give many flowers.　

Common name: Pistia
scientific name: Pistia stratiotes L.,
another name: water lettuce
origin: South America, Africa, Habitat: around warm temperate zone-while detesting the rosette-like tropical regions, environment: Lakes, rice fields, rivers, leaf: oval, lettuce, leaf color: light green, flowers bloom: leaves gaps, both flower and inflorescence shape: small spathe spadix meat and flower piece: no, flowers (agglutination) color: light green, Flowering period: May-October (in the warm area's anniversary), fruit: berries, note: invasive alien species, lettuce named is not edible.