lo FRUIT TREES AND THEIR ENEMIES 



branches produce the appearance of a downy covering 

 over the object attacked, familiar to us in the form of 

 mildew or mould. The branches and spore receptacles 

 constitute, in the larger fungi, the portion of the plant 

 which is commonly called the fungus itself, such as 

 the puff-ball, mushroom and toadstool. 



The mycelium of a fungus also produces other spores, 

 known as perithecia^ which are often formed inside 

 the host plant, and these are enclosed in a tough, 

 leathery receptacle, which renders the destruction of 

 them very difficult. These are the winter, or resting 

 spores, and they are capable of resisting the most 

 intense cold without being injured, and may remain 

 unchanged for years, starting into activity only when 

 they find themselves placed under favourable circum- 

 stances. This, as a rule, is in the spring. 



A fungus, however, besides reproducing itself by 

 means of spores, does so, also, more directly by means 

 of its mycelium, parts of this becoming changed, and 

 hardened into what is called sderotm, In which con- 

 dition it passes the winter, and develops in the follow- 

 ing year, spreading Itself through the soil and attacking 

 fresh plants. 



Fungi which attack living plants — pai^asites — are, 

 naturally, of more importance to the fruit grower than 

 those which feed on dead tissue — saprophytes ; but 

 the two classes sometimes merge into each other, 

 and a fungus which is usually a saprophyte may, 

 under altered conditions, become a parasite, and attack 

 living plants. In some cases, also, a parasitic fungus 

 only reaches the seeding stage on the dead wood of 

 the plant which it has killed. 



