LABORATORY MANUAL OF PHYSIOLOGY. 



spores. The former are produced by the division of the cell con- 

 tents into two or four ovoid masses. These are set free through 

 the resorption of the mother cell membrane, develop two cilia at 

 opposite poles, and become free swimming forms. Later, a cell 

 envelope is also formed. The microspores are smaller, more nu- 

 merous, and are devoid of cell wall. Both forms, finally come to 

 rest, lose their cilia, develop a thick cell wall, and again assume 

 the vegetative condition. 



Sunlight is essential to the growth of this plant as it is, in fact, 

 to all chlorophyll plants. It is through the agency of the chloro- 

 phyll that carbon dioxide is broken down into carbon and oxygen 

 for the constructive metabolism of the plant. This is a distinctive 

 characteristic of the algae and other chlorophyll plants as com- 

 pared with the non-chlorophyll plants, such as the fungi. 



Practicum. Spread out some mud, containing protococcus, on 

 a glass slide, dilute with water, and look for the plant with a low 

 power of the microscope. Study with a high dry lens. Make 

 out the following points- size; form; structure; zoospores. Stain 

 with iodine. This kills the cell and may show the cilia. 



Into two tubes, filled with and inverted over mercury, introduce 

 some water rich in protococcus. From a carbon dioxide genera- 

 tor, introduce into each tube a few bubbles of the gas. Place one 

 tube in the dark and the other in the light. After several hours, 

 examine the tubes. Measure the gas in both. Place a small piece 

 of KOH in each tube. Is the gas absorbed ? In the tube that has 

 been in the light, introduce a few drops of pyrogallic acid solution. 

 Is any more gas absorbed ? Explain. 



Place some water, containing numbers of zoospores, on a slide; 

 cover with a long cover slip and place under the microscope. With 

 the substage mirror, cause a beam of bright sunlight to pass 

 through the specimen. What is the effect on the movement of the 

 spores ? Now reduce the intensity of the light. What is the effect ? 



2. Spirogyra. This form is commonly found, during the sum- 

 mer, in ponds and tanks, as floating masses of a light green color. 

 These masses are found, on observation, to consist of long, fine 



