. Principles of modern biology. Biology. The Plant Kingdom - 601. Fig. 31-6. Two of the red algae (Rhodophyta). Many red algae live in deep quiet waters. These have a deli- cate form, such as is displayed by Dasa plumosa (left). However, some, such as Rhodomenia palmata (right), live in the more agitated tidal zone and these are apt to show a sturdier form. (Courtesy of the American Mu- seum of Natural History, New York.) adding another layer of stony material, may gradually build up and extend a reef enor- mously. Moreover, the algae provide an effec- tive hiding place for coral animals (p. 6
. Principles of modern biology. Biology. The Plant Kingdom - 601. Fig. 31-6. Two of the red algae (Rhodophyta). Many red algae live in deep quiet waters. These have a deli- cate form, such as is displayed by Dasa plumosa (left). However, some, such as Rhodomenia palmata (right), live in the more agitated tidal zone and these are apt to show a sturdier form. (Courtesy of the American Mu- seum of Natural History, New York.) adding another layer of stony material, may gradually build up and extend a reef enor- mously. Moreover, the algae provide an effec- tive hiding place for coral animals (p. 634), which likewise deposit vast amounts of cal- careous materials. Some red algae are used as food. The Japanese cultivate one kind (Porphyra) in carefully tended submarine gardens; and the Scotch are fond of dulse (Rhodymenia, Fig. 31-6), boiled in milk. Moreover, agar, which is so widely used in preparation of bacterial culture media, is derived from two kinds of red algae (Gelidium and Gracilaria); and carrageenin, a material extracted from Irish moss, is useful in the preparation of choco- late milk products. None of the red algae has flagellated re- productive cells, which are so usual among aquatic plants. Typically the nonmotile sperm are carried by the oceanic currents until some are picked up by a sticky pro- tuberance (the trichogyne) from the egg- forming organ. Frequently there is an alter- nation of sexual and asexual generations. The spores of the Rhodophyta are nonflag- ellated. The Schizomycophytes (Bacteria). These exceedingly small, unicellular fungi1 were discussed at some length in Chapter 10. It appears likely that the bacteria orig- inated earlier (p. 566) and that they are more primitive than the blue-green algae, which they tend to resemble. However, bacteria 1 The term fungus (plural, fungi), is a very con- venient one, even though it does not designate any single phylum or other taxonomic group. In fact, all relatively simple colorless (lacking chloro
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