ROT-FUNGI AND THEIR WORK 75 



boring insect. From this mass there is sent out 

 a more or less highly differentiated and completely 

 formed body, the purpose of which is to develop 

 and disseminate the spores. The appearance of 

 sporophores on a tree is of course conclusive evi- 

 dence of the presence of decay within the tree, and 

 usually a large amount of decay, for the fruiting 

 bodies are not produced until the fungus plant has 

 made a strong growth. In certain cases sporo- 

 phores are not produced until the mycelium has 

 exhausted the available supply of nourishment. 

 Frequently a fungus subsisting in a living tree does 

 not send out sporophores until its host dies. The 

 moral is, not to suppose, just because there are no 

 mushrooms on your trees, that there is no decay 

 inside of them. 



The many hundred rot-producing fungi affect- 

 ing living trees fall readily into four groups, ac- 

 cording as they attack mainly the bark, sapwood, 

 heartwood, or roots. For the present purpose it 

 will be enough to describe one or two of the more 

 important members of each group. Readers who 

 desire fuller information are referred to the 

 bibliography. 



Of bark decays the commonest and best known 

 are the apple bark rots and the chestnut bark dis- 

 ease. There are a number of fungi which kill 

 larger or smaller areas of the bark on apple limbs 

 and twigs. Several of them, as the bitter rot, also 



