101 



lengthening the filament, which may break up into frag- 

 ments, each fragment forming a new filament. 



Although Oscillatoria is regarded as a filamentous colony 

 of individuals, the peculiar waving and gliding movements 

 of the filament show the cells working to- 

 gether. The transition from a colony of 

 one-celled independent individuals to an 

 individual of many interdependent cells 

 is insensible and indefinite. 



61. Conclusions. These three forms 

 of blue-green Algae will serve to illustrate 

 the general features of the whole group. 

 The name of the group refers to the fact 

 that in addition to the chlorophyll the 

 cells contain a characteristic blue color- 

 ing matter which does not mask the 

 green, but combined with it gives a 

 bluish-green tint to the plants when 

 seen in masses. Not all the blue-green 

 Algae are bluish-green in tint, however; for the presence 

 of other substances may disguise it, and the color may be 

 yellow, or brown, or even reddish. For example, the 

 largest of all the blue-green Algae has given name to the 

 Red Sea. 



The group is sometimes called the green slimes on ac- 

 count of the characteristic slimy, mucilaginous walls. They 

 are very simple, being one-celled plants, the cells occurring 

 singly or in chains and filaments. The reproduction is 

 exclusively by means of cell-division; and since the cells 

 that divide are ordinary working cells, this method of re- 

 production is usually called vegetative multiplication. In 

 plants whose bodies are many-celled, cell-division usually 

 results in the growth of the individual rather than in the 

 formation of new individuals. The power of motion is 

 * marked in certain forms, and there is also a tendency 



Fio. 94. Oscillatoria: 



A, group of filaments; 



B, a single filament 

 more enlarged. 



