70 MANUAL OF TREE DISEASES 



since they are very light and buoyant. Millions of spores are 

 disseminated from a single fruiting-body during a few days 

 after they become mature. They are somewhat sticky and 

 adhere to any object with which they come in contact. The 

 larger part of them never reach suitable places where infection 

 may be accomplished. However, a sufficiently large number 

 is produced that a few usually find lodgment where infection 

 is possible. Woimds such as the splintered ends of the branch- 

 stubs which hold moisture readily are most likely to become 

 infected. The spores are very short-lived and suitable con- 

 ditions of moisture must be encountered in order to have ger- 

 mination take place. The germ-tube of the spore produces short 

 branches of mycelium which immediately begin the decay of 

 the wood at the point of infection, and as soon as a firm foot- 

 hold is gained, a copious growth of the mycelium occurs, which 

 spreads rapidly. 



Control of wood-rots. 



Wood-rot diseases are more abundant and destructive in 

 the forest than in individual trees grown for shade or ornament. 

 Conditions in the forest are ideal for the development of these 

 fungi. All sorts of wounds are available for infection and thus 

 dissemination and germination of the spores is more efficient 

 in causing a higher percentage of infection. Another factor 

 which makes wood-rots more serious in the forest is that great 

 quantities of fallen trunks and branches are present on which 

 fruiting-bodies of most of the wood-rot fungi continue to be 

 produced in great abundance. Outside the forest, the absence 

 of these condij;ions makes infection less common. A few of 

 the wood-rots, however, are important diseases of shade-trees. 



In controlling' these rots, tree surgery methods are effective 

 if the wood-rot is not too far advanced and if the expense is 

 consi^red justified by the value of the tree. The methods 

 for eliminEtting heartwood- and sapwood-rots are discussed under 



