EXERCISE 92 

 SPIROGYRA THE POND SCUM 



Materials. Abundant in most parts of the country as a frothy 

 green scum on the surface of shallow pools. Fruiting material, when 

 found, should be preserved in formalin. 



Directions for work. With the forceps remove and mount a 

 few of the plants. As you are securing the material note the 

 length of the filament and its appearance to the naked eye. 



In studying the filament under the microscope note the 

 arrangement of the cells and whether they seem to be definitely 

 attached to each other. Also, is there any differentiation between 

 different parts of the filament, or are all parts alike ? 



Study several cells in detail: observe (1) cell, (2) peculiar 

 spiral chloroplast (one or more), (3) cytoplasm (lining the cell 

 wall, very transparent, best seen after staining with iodine), 

 (4) nucleus (imbedded in an irregular mass of cytoplasm near 

 center of cell). This mass of cytoplasm is suspended by delicate 

 threads running from it to the cytoplasm next the cell wall. 

 The space not occupied by the cytoplasm is filled with cell sap 

 (mainly water) and is called the cell vacuole. 



Do you find any cells which, from their length or for any 

 other reason, appear to have been lately formed by division? 

 If so, draw them in outline. 



Draw one or two cells in detail. 



How would this plant secure the essential materials for its 

 nutrition ? Is there any evidence, such as giving off oxygen or 

 presence of starch in the cells associated with the chloroplasts, 

 that it carries on photosynthesis ? Devise your own methods 

 for determining these facts. 



References 



BERGEN and CALDWELL. Practical Botany, pp. 191-193. 

 BERGEN and CALDWELL. Introduction to Botany, pp. 223-225. 



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