NOSTOC 25 



Morphology. The filaments or chains of cells composing 

 nostoc frequently form aggregations as large as marbles. 

 These masses, which contain hundreds of plants, are greenish- 



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FIG. 3. Nostoc. Numerous filaments. Lower right drawing is a filament 

 surrounded by a gelatinous layer. 



* 



blue and, if placed between the thumb and finger are 

 decidedly elastic, particularly when they are left out of water 

 for a few minutes or when they occur on moist soil. If the 

 mass is crushed in the fingers, it is mucilaginous. 



