PRACTICAL WORK. 



No. I. 



THE CELL. 



I. Yeast (Saccharomyces cerevisice). 



Put a small drop of actively growing yeast on a clean 

 slide and cover with a clean coverslip. Examine with a 

 high power and show on your sketch of a single cell, the 

 cell-wall, the protoplasm and numerous vacuoles. Make 

 sketches of budding cells, and of colonies of cells. 



Run in iodine-solution and notice that the wall and 

 protoplasm become stained brown. 



II. Spirogyra. 



i. Mount in water a few filaments of Spirogyra, and 

 note under a low power that each filament consists of a 

 single row of similar cells. Make a sketch of a single cell 

 under high power, showing 



a. cell-wall, sometimes covered with a layer of muci- 

 lage; 



6. the spiral chlorophyll-body, showing "pyrenoids" 

 at intervals ; 



