SACCHAROMYCES 391 



When grown in sugar-solutions multiplication takes place 

 by the process of budding, each cell sending out one or 

 more " sprouts " or protrusions which grow to the size 

 of the parent and then separate from the latter as new 

 individuals. 



The true yeasts when grown upon slices of potato or 

 moist slabs of gypsum, with little nourishment, form 

 spores, the protoplasm of each cell dividing into two or 



c* vx 



FlG. 57. Beer Yeast (Saccharomyces cerevisia, Meyer), showing 

 budding (a) and ascospore formation (b). 



four portions which surround themselves with thin walls, 

 the whole yeast plant thus becoming transformed into a 

 spore-case termed an ascus, the spores within being 

 spoken of as ascospores (Fig. 57)- 



Many species, races, and varieties of Saccharomyces 

 are recognized : they all break down sugars into alcohol 

 and carbon dioxide gas, forming at the same time small 

 quantities of glycerine, succinic acid and other organic 

 compounds. They hydrolyse or " invert " maltose and 

 other di-saccharose sugars by means of the enzyme 

 invertase which they secrete, but their power of producing 

 alcohol is due to an enzyme zymase which can only be 

 obtained from the cells by grinding them with sand or 

 other fine powder and then subjecting the dead cells to 

 high pressure. 



