CHAPTER XVIII 



FUNGI : BACTERIA, YEASTS, MOLDS, MILDEWS, RUSTS, 

 SMUTS, AND MUSHROOMS 



Although the great mass of material phenomena elsewhere had been 

 brought into apparent orderliness and system, here was a region in which 

 the unscientific imagination rioted in mystery and extravagance. The pene- 

 tration of this realm of obscurity by the discoveries of bacteriology gave 

 the human race for the first time in its history a rational theory of disease, 

 dispelled the myths of spontaneous generation, and set the process of decay 

 and kindred phenomena in their true relation to the great cycle of living 

 and nonliving matter. 



The new conception of the microscopic underworld which bacteriology 

 brought into biologic science must be reckoned as a conspicuous landmark, 

 and, in so far as it has changed the attitude of man toward the universe, 

 should be regarded as one of the most important triumphs of natural 

 science. JORDAN, "General Bacteriology," p. 23 



The r&le of fungi in the life of the world. Saccardo's " Syl- 

 loge Fungorum" has described to date 66,615 species of fungi. 

 This means that somewhat more than one fourth of all the 

 plants known to science belong in this group, and over 1000 

 new fungi are being described each year. Food supply is the 

 vital problem of plants, animals, and man, and in order to 

 appreciate the position of the fungi in nature we must study 

 the continual flow of food material and try to understand how 

 the world is fed. 



Fungi lack chlorophyll ; hence they are dependent for food 

 upon other plants and upon animals. Some tend to be omnivo- 

 rous, like the common molds of the household, and take almost 

 any food that comes their way, while others are close feeders, 

 living on some one animal or plant or even upon certain 

 organs, tissues, or substances produced by their necessary 



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