MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 383 



and in various ways, often in vast numbers, more simple bodies 

 which are known as spores. 



In combating apple diseases caused by fungi, the chief object 

 is to prevent the formation of these spores, or if they are formed 

 to destroy them before they can germinate and gain a foothold 

 upon healthy fruit, foliage, or wood. This is more frequently 

 brought about by destroying the diseased portions as soon ■ as 

 observed and by coating or spraying the healthy parts with some 

 substance which will prevent the germination and destroy the 

 spores if by chance they fall thereon. 



The threads of many fungi are colorless, while others are 

 more or less colored or darkened, but all are devoid of the green 

 coloring matter which enables the higher plants to manufacture 

 their food substances, through the aid of energy obtained from 

 sunlight, from the simpler compounds which they get from the 

 air, soil and water. Hence fungi and bacteria which are also 

 deficient in green coloring matter must depend upon more com- 

 plex organic bodies to supply their food materials. Through 

 the action of various ferments which they produce, parasitic 

 fungi can break down and destroy, with varying degrees of 

 ability, the tissues, of their host plants. The results of this 

 decomposition furnish them the food materials necessary for 

 their maintenance and growth. The threads of a wood destroy- 

 ing fungus may be penetrating deep into the interior tissues oi 

 an apple tree, causing their death and decay with very little 

 evidence of disease upon the surface. In fact the conspicuous, 

 external symptoms do not as a rule appear till the fungus ha« 

 used up considerable of the available food material and throws 

 out fruiting organs on the surface. . ,.,!: j . 



Those fungi and bacteria which are able to attack living 

 bodies are said to be parasitic or parasites. Those which secure 

 their nourishment from dead organic matter are designated as 

 saprophytic or saprophytes. The saprophytes far . outnumber 

 the parasites and the majority of them cannot under any con- 

 dition cause disease. However, there is no hard and fast line 

 between the two classes. Some fungi which ordinarily live as 

 saprophytes may, under favoraljle conditions, attack and destroy 

 living plant tissues. ., Some, fungi are obligate parasites but a 

 large number of the disease producing forms are capable of a 

 saprophytic mode of existence as is shown by the fact that they 

 may be successfully grown upon a variety of artificial culture 



