FUNGI 191 



long would it take a pair of elephants to multiply to a mass 

 of the same weight ? 



Size. As we have seen, mere size counts for little. Bac- 

 teria, the smallest plants known, are infinitely more powerful 

 than sequoias or whales. Fungi range in size from the giant 

 puffball (the fruiting body of which may grow to three or even 

 four feet in diameter) to microscopic bacteria, and some of 

 these are quite possibly too minute to be visible under our 

 best microscopes. In the fruiting portion of a large mushroom 

 we see but a small part of the whole fungus. This consists, as 

 we shall see later, of a feltwork of microscopic threads (the 



B 

 FIG. 92. Size of microscopic fungi 



Comparative size of : A, a, molds ; b and c, yeasts ; d, bacteria equally magnified ; 



B, e, minute particle of dust ; /, point of finest cambric needle ; g, bacteria under 



less magnification. After Conn 



feeding, or vegetative, portion), which permeate the soil, leaf 

 mold, wood of a tree, or other substance in which the plant is 

 growing, possibly for many feet in every direction. 



Yeasts (Saccharomycetes, the sugar fungi saccharon, "sugar"; 

 myces, "fungus"). Yeasts are the " sweet tooth" fungi, and 

 their -work in nature is to break down sugars by the process 

 known as fermentation. The end products are alcohol, carbon 

 dioxide, and various oils and flavors characteristic of different 

 species of yeast. The process of fermentation is represented 

 by the following simple chemical equation : 



Sugar Alcohol Carbon Dioxide 



Size and color. Common yeast plants are spherical or ellip- 

 soidal bodies about - of an inch in diameter; a cake of 



