28 AGRICULTURAL BACTERIOLOGY 



cell. A portion of the nucleus passes into the minute pro- 

 tuberance, which then enlarges, and is separated from the 

 mother cell by a constriction. The daughter cell may re- 

 main attached, or may separate at once from the mother 

 cell. 



Spore production in the case of the true yeasts is a method 

 of increase in numbers, since, as a rule, more than one 

 spore is produced, from two to eight being usual. The 

 spores are often termed ascospores, and the spore-producing 

 cell an ascus. The spores are not normally produced in 

 growing cultures. .They have various shapes and markings. 

 In one species, Saccharomycetes anomalus, they are shaped 

 like a derby hat. The ascopores germinate by swelling, 

 bursting the wall, and budding. The true yeasts are those 

 that reproduce by budding and spores. The false yeasts 

 do not produce spores. The term torulce is often applied to 

 the latter. 



The yeast spores are not so resistant to heat as are the 

 bacterial spores ; indeed they are but little, if any, more re- 

 sistant than the vegetative cell. The non-resistance of the 

 yeast spore to heat is of great importance in food preserva- 

 tion. 



Molds. The molds represent a more highly developed 

 and more complex group of organisms than do the bacteria 

 and yeasts. Many hundred genera are known. It is possi- 

 ble to give only a few of the more important points of their 

 morphology, especially of those that are of practical impor- 

 tance. The molds are multicellular, and exhibit a division 

 of work among the cells. Some are concerned with nutri- 

 tive processes, others with reproduction. 



The mold plant consists of a network of branching 

 threads, called hyphw. The threads are formed by cylindri- 

 cal cells placed end to end. The threads concerned with nu- 

 trition are termed vegetative hyphce; those concerned with 



