190 SHADE-TREES IN TOWNS AND CITIES 



fruiting bodies appear and the older ones grow in size. The 

 rotting of the heart- wood continues until the tree, checked in 

 growth and become a mere shell of weak sapwood, is broken 

 off by a windstorm and its existence terminated. 



There is no cure for diseases caused by wound parasites 

 after the fungi enter into the interior of the tree. For a few 

 years there may be no apparent injury, but with the lapse 

 of time the tree becomes badly decayed if not destroyed. 

 The only practical measures of controlling these fungi are 

 of a preventive nature. All broken and dead branches of 

 trees should be removed as quickly as possible, and all 

 wounds, either natural or as a result of pruning, should be 

 covered with tar. The destruction of the fruiting bodies as 

 they appear helps to check the spread of the diseases. 



Sulfur Polyporus {LcBtiporus speciosus (Batt.) Murrill) 

 {Polyporus sulphureus (Bui.) Fr.). — The sulfur polyporus 

 has a very wide distribution, and is important because it is 

 found chiefly on the oaks. It also occurs on the apple, ash, 

 birch, butternut, hemlock, locust, and pine. It is a wound 

 parasite like the false-tinder fungus, and grows on living 

 trees. The mycelium rots the heart of the tree and the fruit 

 bodies grow from knot-holes, and also arise from portions 

 of the trunk killed by the fungus. 



The sulfur polyporus is easy to recognize because of 

 the yellowish color of the soft, spore-bearing bodies. They 

 form a series of shelves overlapping one another. Some- 

 times they form very close together, so as to produce a 

 large, round mass about the size of a person's head. The 

 fruiting bodies of this fungus rarely remain on the tree for 

 any length of time, because they are attacked by insects 

 which destroy them. The fungus is also eagerly sought by 

 mushroom hunters on account of its excellent edible qualities. 



