A MANUAL OF BOTANY 95 



An experiment. Soak some pleurococciis powder in al- 

 cohol, in a vial overnight, and study at the next laboratory 

 period. Observe the color of the alcohol, and of the pleuro- 

 coccus cells (/ii>). What conclusions do you make ? 



Some final questions. 1. How simple may a plant be and 

 yet do all that is necessary for life and reproduction ? 



2. What would you say as to whether pleurococcus has 

 any " old age " or not ? 



3. Why is this plant so universally distributed? 



4. How small, actually, is pleurococcus ? 



Tyi'p:s 2 AND 3. Nostoc axd Oscillatorta (or Lyxgba) 



Habitat. These algjc may be found in still water, espe- 

 cially if somewhat impure. Both may be given to you pre- 

 served in formaldehyde solution. There are many forms, 

 particularly of oscillatoria. 



Nostoc colony. Examine a nostoc colony (the jelly-like 

 mass), and observe its color, form, size, and consistency. 

 What does the naked eye reveal, if anything, in the interior 

 of the mass ? 



Nostoc structure. Prepare a temporary mount and ex- 

 amine with the (hj)). Observe, scattered through the jelly 

 film, numerous necklace-like threads (filaments). Examine 

 carefully for color, and shape of cells, and their variation 

 in size and number in the necklace. How does the color 

 compare with that of the pleurococcus ? Are the cells larger 

 or smaller than in that algie? Observe in particular larger 

 cells and their position in the filaments. How do you ex- 

 plain the varying position ? How may this alga multiply ? 

 What use may the jelbj have ? 



Drawings of noctoc. ])ia\v to show the results of your 

 observation. 



Oscillatoria. Examine oscillatoria or lyngba with the 

 naked eye. What do you find regarding the general ap- 

 pearance ? 



