1895. MICROSCOPICAL JOURNAL 149 



ing the middle of October but few actively rotting plants 

 were found, and many in which the disease had made 

 considerable progress^ ceased to spread. There were no 

 other indications of rot, except that the roots were hollow. 

 Closer examination showed that, surrounding the rotting 

 area, there had been formed by the plant, cork, which 

 protected it. The formation of cork to protect plants 

 from an invading enemy is well known in such diseases 

 as apple scab and potato scab. The spread of this disease 

 seems also to have been influenced somewhat by the age 

 of the plant. Early and very late sown, resisted the 

 disease somewhat better than those planted between the 

 two. 



Soil seems not to have been a factor in influencing the 

 disease. 



. ' CAUSE OF THE DISEASE. 



A large number of roots were examined, but in no case 

 could the mycelium of a fungus be found, except where 

 the disease was well advanced. Innumerable bacteria 

 were always found in the decaying substance. These 

 were always found in the black areas of the root, so 

 that the disease seemed to be of bacterial origin. To 

 test this matter several sound rutabagas in the field were 

 inoculated on the side and in crown. The result shows 

 that the rutabagas began to rot in the course of a few 

 days. Mr. Rolfs then inoculated something more than 

 twenty in the same way, with positive results. I am well 

 aware that this is by no means a crucial test, for the 

 rutabagas may have been affected with the rot, but this 

 we could not detect. It is a well-known fact that bacteria, 

 as well as higher fungi, may at times cause decay and 

 rot as a result of mechanical injuries. 



The next step was to isolate the germ from rutabagas, 

 as well as yellow turnips, which would produce this rot. 



