PLANT PATHOLOGY. 187 



the evil effects of mutilation of the roots are manifest. Where 

 a tree has rotten roots it can not secure a sufficent supply of 

 water and food matters from the soil, so that it suffers from 

 thirst and starvation, w^hile at the same time it is liable to still 

 greater injury by being blown over by severe winds. Allied to 

 the fungi which produce root rot and possibly identical with 

 them are those producing stem rot. They gain access through 

 wounds and penetrate the stem tissues, turning them into a 

 mass of decay. Aside from the weakness of stem, making 

 them especially liable to injury in high winds, the trees so at- 

 tacked show evidence of general thirst and starvation. 



Many fruits are attacked by rot-producing fungi, as in the 

 common apple rot, where a fungus gains entrance through some 

 puncture or wound in the skin, and then penetrates all the tissues 

 of the fruit, eventually turning the whole into a rotten mass. 



GENERAL NATURE OF FUNGI. 



It is not enough to know how a fungus acts in attacking a 

 plant. While that is essential, it is by no means sufficient to 

 enable the fruit grower to know what to do to eradicate it. We 

 must know how and when it reproduces itself. Now every 

 fungus at some time in its life produces tiny seeds (spores) so 

 small that they are easily carried by the wind for considerable 

 distances. No fungus comes spontaneously any more than do 

 weeds or grass. Every one comes from a seed just as every 

 tree comes from a seed. It is these minute seeds that blow 

 from plant to plant, and from tree to tree, thus carrying the 

 disease. 



Now it is a well established fact that every fungus is much 

 more easily combated if taken when it first appears than after 

 it gains full headway. It is with fungi as it is with weeds in 

 your garden:— you can kill them best when they are young, and 

 it is a pretty big job to kill them after they are tall and pretty 

 well rooted. It is important therefore that the fruit grower 

 should know when and where the fungi begin their work on his 

 trees and fruit, for this is the best time to spray with Bordeaux 

 mixture in order to kill the largest number of fungi. Still 

 another reason why the fruit grower should quite certainly 



