and Laboratory Methods. 1897 



XIII. Spirogyra Sp. Class, Conjugatae. Order, Mesocarpales. Family, 

 Zygnemaceae. 



Spirogyra grows in stagnant water or slowly flowing streams, forming floccu- 

 lent, floating masses of a bright green color which are slimy to the touch. 



1. Study naked eye characters, noting that the mass is made up of slender 

 free threads or filaments. 



2. Mount a few filaments in water and examine under low power. Notice 

 the cells with spiral chromatophores (chloroplasts). Shape of the filaments and 

 cells ? Count the number of cells across the cover-glass (^ inch across). How 

 many ? Measure a long filament and estimate the number of cells it con- 

 tains. 



3. Draw part of a filament under low power showing ends, cells, and chro- 

 matophores. Any difference between the two ends ? Describe. 



4. Under high power, draw a cell showing the wall, spiral chloroplasts, 

 pyrenoids, nucleus, and nucleolus. How is the nucleus connected with the 

 other parts ? 



5. Draw a part of a chloroplast showing details of the margin and the 

 pyrenoids. 



6. Treat with salt solution. Draw and describe what takes place. 



7. Study the conjugation from fresh material, or if this is not at hand, from 

 material preserved in Petit's solution or from mounted slides. Notice two fila- 

 ments side by side and that all the zygospores are in the cells of one filament, 

 while the cells of the other filament are empty. This indicates a slight differen- 

 tiation of sex individuals. Draw a piece showing a number of conjugated 

 cells. 



8. Draw two conjugated cells showing all details carefully, especially the 

 zygospore and the conjugation tube. 



9. Draw two cells in which the contents of one cell are passing through the 

 tube. 



10. Draw two cells in which the two 

 rounded processes from the sides have just 

 met. 



11. Draw two cells in which the two pro- 

 cesses are just beginning to develop. 



12. Describe fully the process of conju- 

 gation as observed above. 



13. Make a diagram showing the life 

 cycle by means of diagrammatic figures of 

 the plant, cells and spores. p^^ st-Life Cycle of Spirogyra. 



14. Make a diagram showing the an- 

 cestors of one spore for five generations ; take no account of vegetative propa- 

 gation or of the possible close relationship of conjugating individuals (see Fig. 

 3). Compare with Pleurococcus. 



Ohio-State University. JOHN H. SCHAFFNER. 



etc _r] 



