H4 



BACTERIA IN RELATION TO PLANT DISEASES. 



Nothing is visible in the field corn inoculated at the same time as the sweet corn, i. c, there are 

 no signs of disease. 



May 22, 1905. Cut and examined field-corn plants labeled 8, 10, 11, 12, 39, 40, 41, 42, 44, and 46, which were 

 drying up (the corn is ripening). None of them showed any signs of disease in the stem except numbers 42 and 44. In 

 the stems of these two plants a few of the vessels were found occupied by the yellow slime, but only a few, the infection 

 being slight and confined to the vicinity of the inoculated leaves. This also shows that it is possible to inoculate the 

 disease into field corn, but in general it appears to be much less susceptible than the sweet corn. The variety was not 

 Nelson's Yellow. 



As we have seen, it is a frequent movement of the bacterium to grow out into the husks 

 surrounding the ear and then come to the inner surface, thus affording a very favorable 

 opportunity for the contamination 

 of the surface of the kernels. In 

 this connection the following field 

 observations are of interest : 



INFECTED SEED AS A MEANS OF 

 DISTRIBUTION. 



In the summer of 1903 the 

 writer found this disease in two 

 places in Washington under circum- 

 stances which pointed to seed-corn 

 as the carrier of the pathogenic 

 organism, and the Congressional 

 Seed Distribution as the agent of 

 dissemination. Although these in- 

 ferences were not clinched by the 

 actual demonstration of Bacterium 

 stewarti on or in the suspected seed- 

 corn, the circumstantial evidence is 

 nevertheless so strong as to be worth 

 recording at some length. This 

 evidence is the more credible be- 

 cause the organism is often found in 

 the vascular bundles of the cob, and 

 may penetrate from these into the 

 base of the kernel (see figs. 45, 46, 

 47, 48), and because, as already 

 recorded, it occurs very frequently 

 in the inner husks and shows a 

 strong tendency to come to the sur- 

 face of these organs as a wet slime, 

 which might easily contaminate the 

 surface of the kernels and has been 

 seen so contaminating them by Stewart on Long Island and by the writer in Washington 

 (figs. 49- 50, 51, 5 2 > 53)- 



FIELD OBSERVATIONS OF 1903. 



On July 18, 1903, the writer, greatly to his surprise, discovered one typical case of the 

 Long Island sweet-corn disease (Bad. stewarti) in the garden of Mr. Brown at Takoma Park, 



Fig. 45/ 



*Fig. 45. Bacterium stewarti in sweet corn. Flats, 1902. Vertical section through two kernels and a portion of 

 the cob, showing the relation of parts: A, Floral bract; B, C, Scales of the perianth. Those bundles of the cob in 

 which the bacteria are abundant are drawn in solid black. Bacteria also occur sparingly in the base of each kernel at 

 X, X. This section pas les nearly at right angles to that shown in fig. 57 and, therefore, does not include the embryo. 

 Slide 478 (6, stained with pyronine and methyl violet. Drawn from a photomicrograph, but with various details 

 strengthened. Section torn in places, as at A. For the appearance of D under a high power see fig. 46. 



