LABORATORY AND FIELD WORK 397 



5. Draw a single cell, showing all the parts that you can see. 



6. Draw in outline colonies of two and of four or more cells. 



CHAPTER IV 



Baker's yeast or any of the various yeast cakes or fresh compressed 

 yeast may be used for this study. Brewer's yeast, if it is to be had, is 

 preferable, and especially " top " yeast, which has rather large cells. 

 In many places, however, top yeast is not readily obtainable. 



1. Into a battery jar or other convenient glass jar containing 

 molasses solution (one part of molasses to ten parts of water), drop 

 a cake of compressed yeast or a similar amount of whatever yeast 

 is used. Cover the jar, set it in a warm place, and observe it as 

 often as possible for two or three days. 



2. Soon, probably within a few hours, bubbles of gas will be 

 seen rising to the surface of the liquid. What changes take place 

 in the appearance of the liquid? Does it remain clear? Does a 

 scum form on the surface ? 



3. Notice the odor of the liquid after a day or two. To what is 

 it due ? 



4. When the bubbles are rising freely, mount a drop of the liquid 

 and examine it under the microscope. It will be found to contain 

 yeast cells, some single, some in chains. 



5. Study a single cell. What is its shape? Compare it as to 

 size with the bacillus and Protococcus already studied. Is it 

 colored? Has it a wall? What is the appearance of the proto- 

 plasm? Are any bodies visible in the protoplasm? Have any of 

 them a noticeable color? There may be one large, clear space (a 

 vacuole), or perhaps two or three small vacuoles. 



6. Draw a cell on a large scale, showing all the parts that you 

 can see. 



7. Find a cell that has a small projection (a bud) at one end. 

 Find others, showing buds of different ages. What does a bud 

 finally become? How, if at all, is it separated from the larger cell 

 with which it was at first connected? 



8. Draw in outline three stages in the development of buds. 



9. Do you ever find more than two cells connected? Draw in 

 outline the largest colony you find. 



