STRUCTURE OF YEASTS 



59 



WHAT ARE YEASTS 



Yeast plants are always microscopic, no species being 

 large enough to be seen with the naked eye. When these 

 tiny plants are massed together, as in a yeast cake, the 

 mass may form a bulk large enough to be seen. We can 

 see a yeast cake, 

 but the individual 

 yeast plant is not 

 more than ^ of an 

 inch in diameter, 

 and this is far be- 

 low the power of 

 the unaided vision. 

 By the microscope 

 alone we learn that 

 the yeast mass is 

 made up of millions 



Of minute bodies, FlG ; 3 2 - Common yeast very highly magnified. 

 . Figs, a and b show vacuoles; c shows a nucleus 



each of which is an n inside of the yeast cell; d shows a budding 



individual yeast cell with the nucleus dividing ; e shows the cell 

 r>l an t divided, the new cell containing a bit of the 



old nucleus. 



The yeast plants 



are much simpler than the molds. If a bit of a yeast 

 cake be mixed with a little water and examined under 

 the microscope, there will be found what is shown in 

 Fig. 32. There will be seen large numbers of minute 

 oval bodies, sometimes very nearly spherical or sometimes 

 considerably longer than broad. They are quite color- 

 less and nearly transparent, as seen under the micro- 

 scope, but whitish when seen in bulk. They have a 



