PLANTS WITHOUT CHLOROPHYLL 135 



Dry dusting or sweeping will raise dust, which usually contains 

 mold spores. Use a dampened broom or dust cloth frequently in 

 the kitchen if you wish to preserve foods from molds. 



Other Moldlike Fungi. — Mildews are near relatives of the 

 molds found in our homes. They may attack leather, cloth, etc., 

 in a damp house. Other allied forms may do damage to living 

 plants. Some of these live upon the lilac, rose, or willow. These 

 fungi do not penetrate the host plant to any depth, for they obtain 

 their food from the outer layer of cells in the leaf of their host and 

 cover the leaves with the whitish threads of the mycelium. 

 Hence they may be killed by means of applications of some 

 fungus-killing fluid, as Bordeaux mixture.^ Among the useful 

 plants preyed upon by mildews are the plum, cherry, and peach 

 trees. (The diseases known as black knot and peach curl are 

 thus caused.) Another important member of this group is the 

 tiny parasite found on rye and other grains, which gives us the 

 drug ergot. 



Among other parasitic fungi are rusts and smuts. Wheat rust 

 is probably the most destructive parasitic fungus. Indirectly this 

 parasite is of considerable importance to the citizen of a great city 

 because of its effect upon the price of wheat. 



Yeasts in their Relation to Man 



Fermentation. — It is of common knowledge to country boys 

 or girls that the juice of fresh apples, grapes, and some other 

 fruits, if allowed to stand exposed to the air for a short time will 

 ferment. That is, the sweet juice will begin to taste sour and 

 to have a peculiar odor, which we recognize as that of alcohol. 

 The fermenting juice appears to be full of bubbles which rise to 

 the surface. If we collect enough of these bubbles of gas to make 

 a test, we find it to be carbon dioxide. 



Evidently something changed some part of the apple or grape, 

 the sugar, (C6H12O6), into alcohol, 2 (C2H6O), and carbon dioxide, 

 2(002). This chemical process is known as fermentation. 



1 See Goff and Mayne, First Principles of Agriculture, page 50, for formula of 

 Bordeaux mixture. 



