OSCILLATOKIA 85 



2. The structure of cellular envelopes if present. 



8. The detailed structure of a cell ; the color and its distribution. Are 



chromatophores present ? Can you find a nucleus ? How do the cells 



multiply ;' 



73. Oscillatoria.*^ 



A. Place a small mass of material in a watch glass full of 

 water. What is the color ? After a few hours observe the 

 filaments radiating out from the central mass. Explain this 

 habit of growth after the study outlined in B. 



B. Mount material well teased out. Under l.p. note : 



1. The filaments. Are they branched or unbranched ? Are 

 they of uniform diameter ? 



2, The movements of the filaments. Describe and diagram. 



C. Under h.p. note and illustrate : 



1. The cell structure at the tip of a filament and the par- 

 tition walls back of the tip. Compare the length and 

 breadth of the cells. What is their geometrical form ? 



2. Draw a group of cells on a large scale, showing the dis- 

 tribution of their granular contents and the coloring 

 matter. Are chromatophores present ? Can you find a 

 nucleus ? Where are new partition walls formed ? 



3. Note the occasional dead cells. What is the form of the 

 cell wall on adjacent living cells and at the free tips of 

 filaments ? Why should the wall take this form ? The 

 presence of the dead cells weakens the filament, which 

 breaks apart readily at these points. 



4. How do the cells multiply, and how are new filaments 

 formed ? Is cell division confined to any particular region, 

 or is it general throughout the filament ? 



5. Search for a very delicate sheath which holds the cells 

 together in a filament, like paper about a roll of coins. 



D. Should material of Lyngbya be available, it may be studied 

 advantageously at this point in comparison with Oscillatoria. 



E. Dry a mass of Oscillatoria thoroughly, then pulverize and 

 place in a test tube with twice its bulk of water. After 



