CHAPTER XXIV. 

 ALG^ (Continued). 



THE BLUE-GREEN ALG^* (CYANOPHYCE^). 



373. General characters. The blue-green algae include some 

 of the simplest forms of plant life. In some respects the cell is less 

 specialized than in any of the lowest green algce. The chloro- 

 phyll is not in definite chlorophyll bodies, but is diffused through- 

 out the protoplast and is more or less guised or obscured by a 

 blue pigment, cyanin, hence the name blue-green algae or Cyano- 

 phycece (bluish algae). A few of them have brownish or red 

 pigments. The red shimmer of the red sea is caused by the 

 presence of myriads of one of these algae, Trichodesmium ery- 

 thrceum, which has a red pigment. The nucleus is not so dis- 

 tinctly organized as in most plants. According to some the' deeply 

 stained nuclear matter (chromatin) is distributed throughout 

 the cell in granules, while some recent investigations seem to show 

 that there is a definitely organized nucleus but less specialized 

 than in the other algae. The plants exist as single spherical cells, 

 spiral cells, as colonies, and as filaments composed of numerous * 



* To THE TEACHER. In first-year courses it may not be possible to study 

 any of the members of these groups with the aid of the microscope. Where 

 possible, however, some of the members of each group should be at hand 

 for examination, either in the fresh condition, dried and mounted, or pre- 

 served in formalin or alcohol. A variety of species mounted on cards make 

 interesting objects for observation of color, and for general plant form. 

 The rockweed is an excellent type for the browns. In schools located in 

 cities near the seacoast more can probably be done in the study of the browns 

 and reds than in the interior. For ,this reason several types of these are 

 included. In more advanced classes it may be found convenient to include 

 some microscopic study where facilities for this work are provided. The 

 Cambridge Botanical Supply Company, Cambridge, Mass., makes regular 

 collections and shipments for schools during the autumn. 



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