FUNGI 197 



evenly through the mass. If a speck is spherical and clearly distinct 

 from all others, we may pick it out with a sterilized lifter and be 

 reasonably sure that we have yeast plants all descended from a single 

 parent plant that is, a pure culture. 



Diseases caused by yeasts. Quite naturally one species of 

 yeast causes blight of sorghum, and another, a disease of the 

 crocus, and one or two others attack animals and man. 



Molds and mildews. These are the most troublesome fungi 

 of the household. They take everything in the way of food 

 or clothing, carpets, linen, and even books, that they can get 

 their spores on, if conditions, especially of moisture, .favor 

 their growth ; and since they always can get their spores on 

 everything that the air touches, it behooves the home-keeper 

 to see to it that nothing of value is left where dampness, air 

 stagnation, and darkness may permit growth of these little 

 robber plants. Conn's statement is f " If the air of a room 

 becomes damp or ' close,' as we say, it is almost certain that 

 molds will begin to grow upon any organic substance." While 

 in common household parlance molds and mildews are sup- 

 posed to be distinct, the microscope reveals them as identical, 

 the only difference being that they grow less luxuriantly on 

 leather, cloth, and paper than they do on richer and moister 

 foods. 



Botanical position and structure. The word "mold" is 

 merely a popular designation for a variety of different kinds 

 of plants. The term has no botanical standing, but is so 

 firmly fixed in common usage that we cannot improve upon 

 it to designate the somewhat similar felt-like growth that 

 is likely to cover everything damp.' This growth is tech- 

 nically known as the mycelium of a fungus, and when we 

 examine it we find the key to understanding the growth and 

 structure of all the higher fungi, molds, and mushrooms 

 that is, those above the bacteria and yeasts, and some of these 

 form similar mycelia. The single element is a microscopic 



