. Textbook of botany. Botany. A POND SCUM 49. Fig. i8. — Branched green algie: A, Cladophora; B, Vaucheria. composed, like the bread mold to be described in the next chapter, of a single large cell con- taining many nuclei. Most of the thread- like green algae have some form of sexual reproduction, some of them by means of gametes nearly or quite alike, as are those of Spirogyra; others by means of large, passive female gametes and small, active male gametes. 75. Algae of Water Supplies. — The drinking water of cities, whatever its source, is sure to contain some algae, especially if it is sto
. Textbook of botany. Botany. A POND SCUM 49. Fig. i8. — Branched green algie: A, Cladophora; B, Vaucheria. composed, like the bread mold to be described in the next chapter, of a single large cell con- taining many nuclei. Most of the thread- like green algae have some form of sexual reproduction, some of them by means of gametes nearly or quite alike, as are those of Spirogyra; others by means of large, passive female gametes and small, active male gametes. 75. Algae of Water Supplies. — The drinking water of cities, whatever its source, is sure to contain some algae, especially if it is stored in reservoirs. Certain kinds of algffi, of which Spirogyra is one, sometimes multiply very rapidly in reservoirs of city water. This leads to unpleasant results, partly because the mains or pipes may become clogged, but chiefly because when the algas die they decay and give an unpleasant taste and odor to the water. It has been found that the growth of algas in drinking water can be checked by the use of small amounts of copper sulphate, a solution of which will kill the algae even though it is much too weak to be poisonous to htiman beings. 76. Marine Algae. — The salt waters of seas and oceans, like fresh waters, contain an abundance of plant life. Among the inhabitants of salt water are a good many green algae, not, however, including any of the species of Spirogyra. But the most characteristic marine plants (" seaweeds ") belong to the groups of brown and red alg& — so-called be- cause their cells contain a coloring matter, brown in the one case and red in the other, masking the green color of the chlorophyl which is also present. The brown algae include. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Allen, Charles E. (Charles Elmer), b. 1872; Gilbert, Edward Martinius, joint
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