green algae
green algae
1900–05
Based on the Random House Dictionary, © Random House, Inc. 2012.
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| a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question. |
| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
| green algae | |
| —pl n | |
| the algae of the phylum Chlorophyta, which possess the green pigment chlorophyll. The group includes sea lettuce and spirogyra | |
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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green algae
members of the division Chlorophyta, comprising between 9,000 and 12,000 species. The photosynthetic pigments (chlorophylls a and b, carotene, and xanthophyll) are in the same proportions as those in higher plants. The typical green algal cell, which can be motile or nonmotile, has a central vacuole, pigments contained in plastids that vary in shape in different species, and a two-layered cellulose and pectin cell wall. Food is stored as starch in pyrenoids (proteinaceous cores within the plastids). Green algae, variable in size and shape, include single-celled (Chlamydomonas, desmids), colonial (Hydrodictyon, Volvox), filamentous (Spirogyra, Cladophora), and tubular (Actebularia, Caulerpa) forms. Sexual reproduction is common, with gametes that have two or four flagella. Asexual reproduction is by cell division (Protococcus), motile or nonmotile spores (Ulothrix, Oedogonium), and fragmentation.
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