462 THE president's address. 



decay, and a few of the bacteria that have escaped destruction 

 pass into the soil, where they remain until opportunity offers for 

 entering the root of some leguminous plant. 



Plant diseases caused by bacteria, fortunately, are not numerous ; 

 nevertheless, there are some undoubted cases where very destruc- 

 tive epidemics are to be attributed to the agency of these minute 

 organisms. Amongst the most serious may be mentioned a 

 potato disease which has done widespread injury in the United 

 States, and has recently also been observed in this country. The 

 leaves are first attacked, the disease being spread by insects 

 alternately visiting diseased and healthy plants. By degrees the 

 bacteria travel down the vessels of the stem, their progress being 

 indicated by dark brown streaks, and in the end reach the 

 tubers, which first show a zone of brown discoloration a little 

 distance within the skin. Finally the afl:ected tuber decays, and 

 the bacteria remain in the soil until another crop of potatoes are 

 grown, when the attack is resumed. 



Hyacinths and tomatoes are also liable to injury from the 

 attacks of bacteria. 



Jouni. QucLett Microscopical Club, Ser. 2, Vol. VIIL, No. 52, ApHl 1903. 



