THE ALGJE. 



99 



FIG. 57. Spirogyra. .4, one whole cell and parts of two others, showing the 

 spiral chromatophore and, at d, a nucleus with distinct nucleolus suspended 

 in the center of the cell by bands of protoplasm. B, two filaments of a 

 different species of Spirogyra, showing three stages in the process of con- 

 jugation ; the cells dd are just preparing to connect by means of a tube 

 which forms itself from the projecting cell walls ; the cell g has given up the 

 greater part of its contents to the cell opposite ; at e a zygospore has formed 

 from the contents of the two opposite cells. C shows still a different kind 

 of chromatophore, and at e the formation of a zygospore by parthenogenesis. 



branched filaments of uniform diameter ; use a hand mag- 

 nifier if necessary. 



2. Let a quantity of Spirogyra stand in alcohol for a 

 short time. Then notice the color of the alcohol both by 

 reflected and by transmitted light. Describe the colors. 

 Notice also that the immersed filaments of the Spirogyra 

 are now colorless. 



