. CHAPTER IX. 



YEASTS AND MOULDS. 



The organisms commonly designated as yeasts and moulds, though not 

 belonging to the bacteria (Schizomycetes), are of the greatest importance in 

 human economy and play a most active part in life. Some of them are most 



Fig. 63. — Development of Mucor mucedo. a, b, c, d, stages in the formation of the- 

 zygospore; ti, mature zygospore; e,/, endospore formation; ^, endospores; ^, germinating 

 spore, this develops and finally gives rise to new zygospores; i, mucor slightly magnified. 

 This mould is found on stale bread, damp leather, gloves, etc. 



beneficent while others are very injurious to health. The yeast organisms 

 (Saccharomyces) cause the alcoholic fermentations in saccharine solutions. 

 Many of the mould group cause skin and other diseases. They all belong 

 to the plant division fungi. The more important species may be grouped 

 under three orders, as follows : 



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