AUTHOR'S PREFACE 



SINCE the celebrated memoir by Pasteur on alcoholic fermenta- 

 tion, the yeasts have never ceased to assume an ever-increasing 

 importance in agriculture and the industries. The classic investi- 

 gations by Pasteur, followed by those of Hansen, have shown the 

 profit that may result from a methodical study of the various species 

 of yeasts, by a knowledge of the conditions necessary for their develop- 

 ment and biochemical characteristics for application to the fermenta- 

 tion industries. No one may overlook the benefits which came to such 

 industries by the use of pure cultures and selected species, and the 

 avoidance of yeasts which caused defects in fermented products. The 

 fermentologists have also benefited greatly by these methods. Finally, 

 the relatively recent investigations have shown the relationship of 

 yeasts to certain diseases in man and animals. 



From a purely theoretical point of view the yeasts, on account of 

 the facility with which they allow themselves to be cultivated in artifi- 

 cial media, and by the relatively large size of their cells, are especially 

 favorable objects for experimentation upon which very important 

 investigations of physiology, cytology and sexuality have been made. 

 They have contributed appreciably to the progress of general physiol- 

 ogy and biology. 



It seemed useful to me to collect into one book all of the knowledge 

 required on the morphology, physiology and taxonomy group of fungi, 

 and to arrange it in such a manner that the data would be available 

 for biologists, practitioners in industrial work, agriculturalists and 

 physicians. That is what I attempted to accomplish in the little 

 volume published in the Encyclopedic Scientifique under iiie editorial 

 supervision of Dr. Toulouse. 



Professor Tanner, of the University of Illinois, undertook the 

 translation of this book into the English language in order to render it 

 more accessible to American students and American investigators. 

 This is indeed a great honor to me, one which I did not dream of when 

 I prepared this modest work a few years ago. I am very happy to 

 have this indication of friendship between scientific America and 

 France, a friendship which I hope may become stronger and stronger. 

 One sufficiently understands the significance of a scientific alliance of 



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