58 THE BIOLOGY OF THE CELL 



Are they formed in each cell of the fruiting fila- 

 ment? What determines their place of forma- 

 tion? Is there any visible difference, such as 

 would indicate sex, between the two filaments 

 whose cells conjugate to form the zygospores? 

 Look for zygospores in various stages of develop- 

 ment. Can you find the different stages of this 

 process exhibited in a single filament ? What are 

 the details of the process ? What is the shape of 

 a ripe spore? Structure? What is left in the 

 conjugating cells after the zygospore is formed? 

 What significance in the name " zygospore " ? 

 Can the spore pass out of the cell through the 

 conjugating tube ? If not, how can the spore get 

 out ? After the formation of the spore is the cell 

 living or dead ? Notice that the entire cell-con- 

 tents which at one time is " vegetative " becomes 

 " reproductive." 

 Draw a number of cells to illustrate the facts 

 learned. 



PHYSIOLOGY 



In addition to the physiological topics studied in the 

 examination of the reproductive stage of the plant, the 

 following may be investigated : 



A. — Formation of Starch (Assimilation). 

 I. Effect of light. 



a. Take some filaments of Spirogyra whose cells are 

 known to contain starch, place the filaments in a 

 dish of water, and set the dish in a warm, dark 

 place for two or three days, or until microscopic 

 examination shows no starch to be present, being 

 careful to prevent the total evaporation of the 



