374 THE NON-VASCULAR PLANTS 



rophytes, all parasitic or saprophytic plants are not fungi. 

 Some seed plants do not have chlorophyll ; they are as 

 dependent for their food as the fungi are. Indian pipe is 

 a saprophyte, and dodder is a parasite. So the words 

 parasite and saprophyte do not denote a definite group of 

 plants ; they denote a kind of nutritive habit. Some fungi 

 are both saprophytic and parasitic. They take their food 

 wherever they can get it. The plant or animal from which 

 a parasite derives nourishment is called the host of that 

 parasite. 



B. Economic Importance. — To say that a thing is of 

 economic importance to man does not necessarily mean that 

 it helps him. Its importance may be in the way of injury 

 as well as in the way of benefit. Fungi are of huge economic 

 importance to man in both ways. As to injury, certain 

 fungi are the causes of many of the diseases of cultivated 

 crops, of farm animals, and of man himself. As to benefit, 

 they cause the decomposition of organic substances, and 

 increase the fertility of soil. In bread making and cheese 

 making certain fungi are essential. Yeast is a kind of 

 fungus. 



In the process of decomposition complex organic mole- 

 cules are changed into simpler ones. These simpler mole- 

 cules are then available for plant use. The fertility of 

 humus depends chiefly on the activity of bacteria which 

 transform its complex molecules into molecules which 

 plants can use. 



C. Bacteria. — These minute, unicellular organisms have 

 by far the greatest economic importance of all fungi. In 

 some of their characteristics they are different from all 



