72 PRACTICAL TREE REPAIR 



upon living or dead plants or animals. Those 

 which subsist upon living organisms are called 

 parasites; those which live on dead matter are 

 saprophytes. This division, however, is not iron- 

 clad, for some fungi part of the time follow the 

 policy of one class and part of the time that of the 

 other. Fungi which can live only upon the heart- 

 wood of trees are of course really saprophytic, be- 

 cause the heartwood is dead. 



Intelligently to prevent and as far as possible 

 remedy the attacks of rot-producing fungi, it is 

 essential that the man who is doing tree repair 

 work should study and understand their manner 

 of growth and distribution, and should be able to 

 distinguish the most important species, just as a 

 good physician must know all that has been dis- 

 covered about typhus and tuberculosis bacilli. 



The life cycle of a fungus is superficially quite 

 like that of one of the higher plants. The mush- 

 rooms and hoof-like or shelf-like growths we see 

 so often on dead and decayed trees are the fruit- 

 ing bodies of rot-producing fungi. From their 

 lower surfaces come thousands of little dust-like 

 cells, called spores, which have the capacity of 

 vegetating like seeds and of growing into new 

 fungus plants. Let us suppose that such a spore, 

 from the fruiting-body of the " white heart-rot," 

 is wafted away by the wind and falls upon an old 

 bark-wound in the trunk of a maple, the surface 



