1911 Encyclopædia Britannica/Duckweed
DUCKWEED, the common botanical name for species of Lemna which form a green coating on fresh-water ponds and ditches. The plants are of extremely simple structure and are the smallest and least differentiated of flowering plants. They consist of a so-called “frond”—a flattened green more or less oval structure which emits branches similar to itself from lateral pockets at or near the base. From the under surface a root with a well-developed sheath grows downwards into the water. The flowers, which are rarely found in Britain, are developed in one of the lateral pockets. The inflorescence is a very simple one, consisting of one or two male flowers each comprising a single stamen, and a female flower comprising a flask-shaped pistil. The order Lemnaceae to which they belong is regarded as representing a very reduced type nearly allied to the Aroids. It is represented in Britain by four species of Lemna, and a still smaller and simpler plant, Wolffia, in which the fronds are only one-twentieth of an inch long and have no roots.
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1, Lemna minor (Lesser Duckweed) nat. size. |