9 2 



BACTERIA IN RELATION TO PLANT DISEASES. 



Mr. Stewart does not state where his inoculation experiments were performed, but pre- 

 sumably they were all made on Long Island, because in the introduction to this part of his 

 bulletin he says: 



Attempts to inoculate field-grown plants of sweet-corn have been unsatisfactory because it has 

 been practically impossible to obtain plants which were known to be free from the disease. 



I quote below all of Mr. Stewart's statements respecting his inoculations: 



Susceptible varieties have been quite generally affected, and since the disease is one which acts 

 slowly it is not possible to get results of much value from inoculation experiments made upon plants 



Fig. 40.' 



among which the disease previously existed, even to a slight extent. Only one of the field experi- 

 ments is worth reporting in detail. It is as follows: In 1896 thirteen hills of Manhattan sweet-corn 

 were planted in one row. In each of the first seven hills there was placed, at time of planting, a hand- 

 ful of dirt taken from soil in which the disease was prevalent the preceding season. The remaining 

 six hills were left untreated for comparison. When the plants were a few inches high they were thinned 

 to four in a hill. A few of the plants in the inoculated hills began to wither before they were a foot 

 high, and from this time on they withered one by one, until on July 20, when the kernels were "in the 

 milk, " all of the inoculated plants except two were either dead or dying. At this date, not a single 

 plant in any of the uninoculated hills showed any symptoms of the disease ; but later in the season 

 several of the plants became affected. How they came to be affected is not known. While this exper- 

 iment was not wholly satisfactory the results tend to show that the disease is communicable. 



*Fic. 40. Same as fig. 39, but from another plant and enlarged 6 times, to bring out bacterial ooze more distinctly. 



