pond scum
pond scum
1885–90
Based on the Random House Dictionary, © Random House, Inc. 2012.
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| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
| an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle. |
| pond scum | |
| —n | |
| a greenish layer floating on the surface of stagnant waters, consisting of various freshwater algae | |
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Copyright 2007. Published by McGraw Hill.
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pond scum
genus of green algae, found only in fresh water and usually free-floating. The slippery unbranched filaments are composed of cylindrical cells containing one or more beautiful spiral green chloroplasts, from which the genus gets its name. The nucleus is suspended in the central vacuole by fine cytoplasmic filaments. Vegetative reproduction is by fragmentation of the filaments. In sexual conjugation, cells of two strands lying side by side are joined by the outgrowths, or conjugation tubes, and the contents of one cell pass into and fuse with the contents of the other. The resulting fused cell (zygote) becomes surrounded by a thick wall and overwinters, while the vegetative filaments die
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