1700 Journal of Applied Microscopy 



4. In how many directions do the cells divide ? Where and how does cell 

 division take place ? A filament like this is called a linear aggregate. 



5. Reproduction. In old filaments look for the development of hormogones 

 — short pieces of a number of cells broken loose inside of the sheath. Draw 

 and describe. How do the hormogones escape from the sheath ? 



(b) Oscillator ia sp. (Oscillaria.) 



Any of the minute, bluish-green forms which produce slimy, membranous 

 layers in ponds, rivers and creeks may be used. They may be kept for an 

 indefinite time in a covered glass jar of water. 



1. Mount a small flake in water, study under high power, and draw several 

 of the slender filaments. There is no definite sheath present. Describe the 

 color, shape of cells, and cell contents so far as they can be seen. Are the two 

 ends alike? Compare as to size, etc., with Lyngbya. Draw a single cell. 



2. Study the reproduction. Compare with the method of reproduction in 

 Lyngbya. 



3. Make a careful study of the movement of the filaments. To get good 

 results the plants should first be placed for some time in direct sunlight, and the 

 water should not be cold. Describe the movement. Why can these plants 

 move more actively than the Lyngbyas ? 



VII. Beggiatoa alba (Vauch. ) Trev. Class, Schizomycetes. Order, Desmo- 

 bacteriales (Filamentous Bacteria). Family, Beggiatoaceai. 



These plants are usually very abundant in sulphur springs and in shady 

 places in ponds and stagnant water where decaying vegetable matter is present. 

 Beggiatoa may be kept for years in a covered glass jar filled with water, pro- 

 vided there is a layer of decaying vegetable sediment in the bottom. 



1. With a medicine dropper take up some of the black sediment containing 

 Beggiatoa, mount, and examine under high power. Study the slender, more or 

 less hyaline filaments, and draw one carefully. Draw a single cell showing the 

 large sulphur granules. No chlorophyll is present. Describe the plant in 

 general. 



2. Study and describe the movement. Do the sulphur granules move in the 

 cell ? How many seconds does it take for the tip of a filament to travel from 

 one side of the field to the other ? 



3. How does this plant obtain its food, and upon what does it live ? How 

 different in this respect from Pleurococcus ? To what physiological class does 

 Beggiatoa belong ? • 



4. Note. These plants are intermediate between the blue-green alga3 and 

 the bacteria. What relation is there between the lack of chlorophyll and the 

 saprophytic habit ? 



Ohio State University. JOHN H. ScHAFKNER. 



