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

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

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

 parent plant — that is, a pure culture. 



Diseases caused by yeasts. C^uite naturally one species of 

 yeast causes blight of soro-bmn, and another, a disease of ibr 

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



Molds and mildews. These are the most troublesome fun«n 

 of tlie household. They take everytln'ni;- in tlie wav 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 dam[)ness, air 

 stagnation, and darkness may permit growth of these little 

 robber plants. Conn's statement is: "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." AVhile 

 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 tliey do on richer and moisttn- 

 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 l)otanical standing, but is so 

 lirndy fixed in common usage that we cannot improve upon 

 it to designate the somewhat similar fdt-likc growtli that 

 is likely to cover everything dam[). This growth is tech- 

 nically known as the mjiceHum of a fungus, and \\\\v\\ we 

 examine it we find the key to understanding^ the trrowlh and 

 strttcture of all the higher fungi, molds, and nuishrooms — 

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

 form similar mycelia. The single element is a microscopic 



