YEAST. 



DISSOLVE a small piece of compressed yeast in water, 

 mount a drop on a slide and examine with the compound 

 microscope. Or better mount a drop of Pasteur's solution 

 in which yeast is growing vigorously. 



I. Morphology. 



1. Form. What is the form of the yeast cells? Are all 

 cells of the same shape? Are they single or in groups? 

 Are the cells arranged similarly in different groups? Are 

 they uniform in size? Make drawings to show the points 

 observed. 



2. Structure. Is a cell wall present? Note its color and 

 thickness. Is protoplasm present within the cell? Does 

 it show any color? Look for vacuoles within the cell. Is 

 more than one present? Is the size of all vacuoles the same? 

 Is there any difference in size or number of vacuoles in single 

 cells and in groups of cells? Is there any difference in size 

 and number of vacuoles in growing yeast and yeast from a 

 compressed cake. How can this be accounted for? Small 

 glistening oil drops are often present near the vacuoles. A 

 nucleus is present in each cell but it can be demonstrated 

 only by special methods. 



H Physiology. 



1. Reproduction. Examine cells from actively growing 

 yeast and from compressed yeast and note any differences 



