IMPORTANCE OF PLANTS TO MAN 



243 



Those plants which are the most harmful to man 

 belong to a group of plants known as fungi. Many 

 diseases of cultivated crops, of farm animals, and of 

 man himself are caused by members of this group. 

 The plants which belong to the fungi do not have 

 chlorophyll. Consequently they are unable to make 

 their own food and must depend upon other living 

 organisms for securing it. Some of them obtain their 

 food directly from living plants or animals and are 

 called parasites. The plant or animal from which they 

 derive their food is called the host. The parasite attaches 

 itself to its host and sucks out its food supply. Others 

 use non-living substances for food, but these substances 

 were once a part of living organisms. These are called 

 saprophytes. Yeasts, molds, mushrooms, and bacteria 

 are fungi. Of these, bacteria have by far the greatest 

 economic importance. 



Fig. 106. A mold which forms a white furry growth on damp bread. 



Bacteria. The study of bacteria is a special subject 

 called bacteriology. This fact in itself indicates some- 



