GEEEN FELT 271 



ment of the oogonium by examining specimens 

 which show it in various stages of growth. Of 

 how many cells is it composed ? Compare with 

 antheridium. Try to see the manner in which a 

 mature oogonium opens by the top becoming 

 gelatinous. Endeavor to see the antherozoids 

 enter. Examine oogonia which have been fer- 

 tilized. What changes have taken place in the 

 color, shape, and arrangement of the contained 

 protoplasm, or oosphere, and in the cell- wall? Is 

 the oogonium a motile organ ? Is the fertilized 

 oogonium in actual contact with the antheridium? 

 Compare with Spirogyra. What is the structure 

 of the ripe oosphere, now called oospore ? Are 

 there any organs of motion on it ? Compare with 

 the zygospore of Spirogyra. 

 Draw a filament showing the facts learned about the 

 reproductive organs of Vaucheria. 



II. The asexual reproditctive hodies. 



a. The zoogouidia or zoospores. — Place some vig- 

 orous plants in water in a dark place overnight, 

 then examine for zoogonidia early the next morn- 

 ing, or keep the plants in the dark until ready to 

 make the examination. Put some of the plants 

 into a porcelain dish, and with a hand -lens look 

 for filaments having swollen ends. These fila- 

 ments are ready to form zoogonidia. Mount 

 some of these filaments without a cover -glass. 

 How much of the filament is occupied by the zoo- 

 gonidium ? What is the shape of a zoogonidium ? 

 Color ? How does it move ? What are its organs 

 of motion? Where are they situated? What ap- 

 propriateness about the name "zoogonidium"? 



