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 fungi 1 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 chlorophyll) plants 

 are called fungi. 



