ALGA 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 Algz 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 rye. 94.—Oscillatoria: 
green, but combined with it gives a  4,sroupof filaments; 
a _ B, a single filament 
bluish-green tint to the plants when  moreenlarged. 
seen in masses. Not all the blue-green 
Alge 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 Alge has given name to the 
Red Sea. 
The group is sometimes called the green slimes on ac- 
count of the characteristic shimy, 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 
