194 



THE PLANT WORLD 



Chestnut blight. The dead trees along this road have 

 been attacked by the parasite. 



have already seen some- 

 thing of their characteris- 

 tics. They are as much 

 dependent upon the green 

 plants for food as are ani- 

 mals. But some of the 

 fungi require dead organic- 

 matter for their food. 

 This may be obtained from 

 decayed vegetable or ani- 

 mal material in soil, from 

 the bodies of dead plants 

 and animals, or even from 

 foods prepared for man. 

 Fungi which feed upon 

 non-living organic material 

 are known as saprophytes. 

 Examples are the mush- 

 rooms, yeasts, and molds. 

 Some parasitic fungi. Some fungi prefer living plants or animals 

 for their food and are therefore classed as parasites. An example 

 is the chestnut blight or canker, which has killed chestnut trees 

 by the thousands in the eastern part of the United States. It pro- 

 duces millions of tiny spores, which, blown about by the wind, 

 light on the trees, sprout, and send under the bark thread-like 

 mycelia which absorb the food circulating in the living cells, even- 

 tually causing the death of the tree. The chestnut canker, in- 

 troduced from abroad on chestnuts planted near the city of New 

 York in 1904, within ten years had destroyed practically every 

 chestnut tree in the eastern part of the United States. 



Another fungus which does much harm to trees is the shelf or 

 bracket fungus. The shelflike body is in reality the reproductive 

 part of the plant; in its lower surface are formed millions of 

 asexual spores, which, when they fall on a dead or a dying tree 

 trunk, may start a new fungus growth. The true body of the 

 plant, a network of threads, is found under the bark. Once 

 established, it spreads rapidly. There is no remedy except to 



