谁可以用英语介绍有关durkweed?应该是duckweed吧.
权威英语资料：
Duckweeds, or water lentils, are aquatic plants which float on or just beneath the surface of still or slow-moving fresh water bodies. They arose from within the arum or aroid family, (Araceae), and therefore, often are classified as the subfamily Lemnoideae within the Araceae. Classifications created prior to the approximate end of the twentieth century tend to classify them as a separate family, Lemnaceae.
These plants are very simple, lacking an obvious stem or leaves. They consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface, with or without simple rootlets. The plants are highly reduced from their earlier relatives in Araceae.
Reproduction is mostly by asexual budding, but occasionally three tiny 'flowers' consisting of two stamens and a pistil are produced and sexual reproduction occurs. Some view this 'flower' as a pseudanthium, or reduced inflorescence, with three flowers that are distinctly either female or male and which are derived from the spadix in Araceae. Anatomical research regarding the mechanics of this process has not been completed or remains ambiguous due to considerable evolutionary reduction of these plants from their earlier relatives. The flower of Wolffia is the smallest known flower in the world, measuring merely 0.3 mm long.
The fruit produced through this occasional sexual reproduction is a utricle, and a seed is produced in a sac containing air that facilitates flotation.