Lemna
| Lemna {{{latin_name}}}
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| Standard Cyclopedia of Horticulture |
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Lemna (old Greek name, probably referring to the swampy habitat). Lemnaceae. Duckweed. Duck's-Meat. Minute floating plants, like fragments of green, often found in standing pools and sometimes introduced into aquaria and lawn basins. The Lemnaceae comprises the minutest of flowering plants, some 30 species in 4 genera: Lemna, Spirodela, Wolffia, Wolffiella. They are widely distributed in temperate, subtropical and tropical regions. They often cover the water of ponds with a mantle of green. The lemnas and spirodelas are most useful because they are larger and more conspicuous than the wolffias. They are easily gathered for schoolroom and home aquaria, and may be procured from specialists in aquatics and native plants. Ducks and some fish eat these plants. The lemnas are without any distinct stems a whole plant commonly consisting of 1 miniature leaf and 1 unbranched root which has no vascular tissue. These leaves are called fronds by the botanist. The plants grow separately, or cohere by their edges in 2's or 3's, and multiply by similar fronds, which grow out of the edges of the old ones something like buds. The flowers are minute and appear on the edge of the frond. They consist apparently of a pistil and 2 stamens which are enclosed in a sheath, which botanists have determined is a spathe by reason of the place where it is borne and by homology with related plants. Botanists now consider the 2 stamens as 2 flowers. and the pistil a third flower. L.minor is said to flower more frequently than any other northern species. Duckweeds are perennial plants. In the autumn they fall to the bottom of the ditch or pond, but rise again in the spring, and increase in size. The allied genus Wolfiia contains the smallest flowering plants. There are about 10 or a dozen species of duckweeds, widely scattered. L. polyrhiza is now known as Spirodela polyrhiza, but Spirodela is considered by Bentham and Hooker a subgenus of Lemna. The common duckweed occasionally infests the small lily ponds (artificial ones), where it is a pest. The simple remedy is to flush the pond and see that common goldfish or carp are in sufficient numbers to clear off the remainder. S. polyrhiza, Schl. Fronds broadly obovate or orbicular, attaining 3 or 4 lines diam., palmately nerved. Common in U. S.
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Cultivation
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Propagation
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Pests and diseases
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Species
Other species of Lemna are native in N. Amer. Of Wolffia there are also a few species and of Wolffiella one. The wolffias are seldom collected for lawn pondCH.
Gallery
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
