84 STATE POMOLOGICAL SOCIETY. 



cient food, the fungus fruits by sending up little stalks each of 

 which bears a sac called a Sporanginui which contains a large 

 number of spores. 



We have seen that fungi differ greatly in form and in their 

 manner of reproduction. They also differ in the source of their 

 food supply. Some fungi are able to get their food only from 

 dead organic matter and are called saprophytes. The ether 

 class is able to attack living organisms and they take their food 

 from that source and are called parasites. It is with parasitic 

 fungi that we are most concerned in the study of plant diseases. 

 However, in many cases it is only possible to determine whether 

 a fungus is a parasite or a saprophyte by carrying on extensive 

 inoculation experiments. 



Several lines of study have been carried on at the Station in 

 connection with apple diseases. In the summer of 1908 cul- 

 tures of fungi were obtained from apple leaf-spot from orchards 

 in a large number of different parts of the State. In all, 13 

 species of fungi were isolated from the leaf-spot, several of 

 which have been regarded as causes of the disease by Experi- 

 ment Station workers in other parts of the United States. 



Inoculation experiments which were carried on in the early 

 part of the summer of 1909 show that only one of these fungi 

 is capable of causing the leaf-spot on uninjured leaves. When 

 spots in the leaves are killed in some other way, the other fungi 

 are able to grow upon the dead spots as saprophytes. The one 

 fungus which has been found to cause leaf-spot is the same 

 one which causes a rot of the fruit known as "black rot" and 

 also causes one form of canker on the branches. The fact that 

 a single fungus is able to cause disease of leaves, fruit, and wood 

 throws some light on methods of treatment. An old tree which 

 has a large number of cankers on its branches caused by the 

 black rot fungus is almost certain to show a large amount of 

 leaf-spot, and of decayed fruit. The best treatment in such a 

 case is to remove the source of infection by cutting out and burn- 

 ing the dead wood upon which the fungus is fruiting. This fol- 

 lowed by thorough spraying should control the leaf-spot and 

 the decay of the fruit. 



Another line of investigation which has been carried on is in 

 determining the number of fungi which we have in Maine which 

 are capable of causing diseases of the wood which are usually 



