n6 



BACTERIA IN RELATION TO PLANT DISEASES. 



revealed an astonishing condition. On July 21, 15 per cent of the Cosmopolitan corn was 

 diseased by Bad. stewarti and a month later there were 2 1 additional cases, making a total 

 for this variety of 26 diseased plants to 7 sound ones (80 per cent), 7 other plants having 

 disappeared prior to July 21, probably as a result of disease during the seedling stage or 

 soon after. Many other varieties in the plot were more or less diseased. 



The subject was of so much interest that the writer made a trip to Wakeman, Ohio, 

 to learn something more concerning the nature of the "rot" which on good land could 

 destroy four-fifths of a crop of seed-corn. The field on which the Cosmopolitan corn had 

 been grown was then planted to other crops and nothing could be learned from an inspection 



of it. It was a level 

 field of good char- 

 acter. The owner 

 of the field, the man 

 who grew the corn, 

 evidently knew 

 much more than he 

 was willing to ad- 

 mit ; in fact he was 

 so suspicious and 

 secretive when 

 questioned con- 

 cerning the nature 

 of this rot that 

 nothing of any 

 value was obtained 

 from him, other 

 than the unavoid- 

 able inference to be 

 drawn from the 

 way in which he 

 resented all in- 

 quiries. That the 

 rot in his field was 

 due to Bad. stewarti 

 the writer has not 

 the slightest doubt, 

 but it would have 

 been much more 

 satisfactory and 



Fig. 47. 



helpful to agriculture if he had been willing to cooperate in settling the question. 



To return now to the trial plots on the Flats. These were about a quarter mile from 

 my experiments of 1902. Maize had been grown in many varieties, in large tracts, on this 

 farm for several years and this was the first spontaneous appearance of the disease. The 

 chance of its having come from my experiments of 1902 seemed extremely slight. The 

 most reasonable explanation of the appearance of the disease in such a severe form was 



*FiG. 47. Bacterium stewarti in sweet corn. Cross-section of outer portion of a cob, showing how the bacteria 

 have penetrated into the base of the immature kernel. They are only in the vascular bundles and their immediate 

 vicinity (solid black parts). Plant inoculated in August 1902, on tips of the leaves in the seedling stage. Material 

 collected and fixed (in strong alcohol) Oct. 27. Figure drawn with the help of the Abbe camera, but numerous nuclei 

 omitted and also certain indistinct tissues in the angles and around the margins of the lunulate area in which the scale 

 of magnification is placed. Slide 235 B 14. For a detail see Fig. 48. 



