CH. l] YEAST. 3 



purple colour given by this Schulze's fluid is character- 

 istic of cellulose. This reaction must be studied on the 

 cell-walls of the higher plants, because the cellulose of the 

 yeast plant, in common with that of the fungi generally, 

 only gives a purple colour after a certain preliminary treat- 

 ment. 



FIG. 1. 



YEAST UNDEU A HIGH POWER, 

 a g successive stages of budding. 



The yeast-cell as it appears under a high power of the 

 microscope is shown in fig. 1 a. The cells are seen to 

 contain a granular protoplasm in which clear spaces occur : 

 these are cavities in the protoplasm, containing fluid and 

 known as vacuoles : the fluid in the vacuoles is known as 

 cell-sap. 



Reproduction. 



The fact that yeast increases in quantity by reproduc- 

 tion can be demonstrated by adding a minute drop of the 



12 



