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BIOLOGY FOR BEGINNERS 



two edible kinds and use them only, or leave them all severely 

 alone as food. 



Another class of the fungi includes the rusts and smuts which 

 attack grains, corn, and other grasses, doing enormous damage 

 to crops. Mildew is a common fungus whose chief harm is the 

 causing of rot in potato and similar crops, and destruction of grapes 

 and other fruits. Molds are also familiar forms which thrive upon 



FIG. 42. Colonies of budding yeast cells (Sedgewick and Wilson) 

 From Calkins. 



food stuffs, bread, meats, canned fruits, and even wood and paper, 

 if conditions are such that their spores can germinate. 



Yeast plants are a still simpler class of fungi. We use them so 

 commonly that we hardly realize that they are plants at all. Yeast, 

 however, is a true one-celled plant, living on dilute sugar solutions 

 which it changes to alcohol. It sets free carbon dioxide gas as a 

 waste product. Thus yeast is used in two very different kinds of 



