THE PLAisT GKOUPS 



87 



b. Structure of the growing yeast plant. 



(1) Study a mount of the above yeast solution with low 

 and with high powers of the microscope. Is the 

 yeast plant unicellular or is it composed of more 

 than one cell ? Are all the yeast plants on the 

 slide the same in size and in cellular structure ? 



| & 6 







FIG. 20. Various kinds of wine and beer yeasts 



o, fo, wine yeast (S. ellipsoideus) (a, young and vigorous; b, old (1) and dead (2)) ; 

 c, d, beer yeast (S. cerevisise) (c, bottom yeast; d, top yeast). After Marshall 



(2) Select a large unicellular plant and observe its 



minute structure. Is the yeast cell like a root- 

 tip cell ? How does it differ from the cell of an 

 alga like Protococcus ? What fundamental nutri- 

 tive process, performed by Protococcus, is impos- 

 sible for yeast plants ? Draw and name the parts 

 of a large yeast cell. 



(3) How do the small yeast cells differ from the large 



cells in structure ? Draw a small yeast cell and 

 compare with the large cell drawn above. 



