STEWART'S DISEASE OF SWEET CORN (MAIZE). 



Ill 



August 20. The following varieties of sugar-corn were planted: Red Cory, Early Red Cory, Early White Cory, Perry's 

 Hybrid. There were many pots of each. All stood on a bench in one of the hot-houses. 



August 30. Tubes of slant agar, Nos. 9 to 16, were streaked directly from tubes 1 to 8 of July 17 (the agar-stab-cultures 

 brought from Long Island). 



September 3. Masses of the yellow slime from these eight agar-streak-cultures were placed on the tips of the young 

 leaves by means of a platinum loop. On some plants one leaf only was inoculated, on others two. The 

 young plants were 1 to 2 inches high. The work was done between 1 and 3 o'clock on a cloudy afternoon. 

 As soon as inoculated the plants were placed under the bench in the dark. 



September 4, night. The plants remained under the bench about 28 hours. They were then put on the bench. 



September 6. The plants are now about 3 inches high; there are some indications of infection at the leaf-tips, but noth- 

 ing absolutely sure. 



October 18. The first case was brought in and examined to-day. It is the variety known as Red Cory. The vessels 

 are full of the yellow slime. 



October. The second case, a very typical one, was found in the Early Red Cory. A plant of Early White Cory, acci- 

 dentally broken by the gardener, was examined at the same time, but did not appear to be affected. 



December 16. Those plants nearest to maturity were removed and dissected to-day. The culms were so hard that 

 they could be cracked like pipe-stems. The plants were from 18 inches to 4 feet high and quite spindling. 

 Most of the stems were green throughout (internally) and so brittle that they broke apart with a noise when 

 bent at the nodes; even many of the internodes snapped like a dry stick, although the stems were not dead. 

 The diameter of the stems at the base varied from 0.25 inch to 0.5 inch; most were under 0.5 inch. They had 

 produced very few good ears. The plants were specked somewhat with Puccinia maydis, and many of the 

 leaves had dried out, but mostly as a result of unfavorable conditions rather than by reason of the disease. 



January 5. The remainder of the plants were examined to-day. These plants also were very brittle. Many of them 

 were green throughout, though the pith is ordinarily white. Combining the early counts with those of Decem- 

 ber 16 and those obtained to-day, we have the results given in table 8, which should be premised by the 

 statement that yellow bacterial slime was found in the vascular bundles of the stem of all plants marked 

 "diseased." 



Table 8. Results of the Inoculations. 



Series and variety. 



III. Perry's Hybrid. .. 



IV. Early Red Cory. . 

 V. Early Red Cory. . 



VI. Early White Cory 



VII. Red Cory 



Summary 



Diseased. 



'9 



>4 



Free. 



45 

 44 

 30 

 105 

 98 



Total. 



5 

 49 



39 



114 

 103 



322 



355 



* Several with black bundles. 



As a result of examinations with the compound microscope, 6 of the 14 doubtful cases 

 were found to contain bacteria, making a final total of 25 cases. Subtracting 60 check 

 plants from the whole number, we have approximately 8 per cent of diseased plants, against 

 62 per cent obtained in the previous experiment. 



Three of the check plants became diseased. 



These plants were first crowded together for 2 months, or more, on the west side of the 

 house, became too large for the pots, and grew very spindling. This crowding was due to 

 the fact that we had no other place to set them. They were then moved into the middle 

 section of the hot-house, which was much too warm for them. Some of them were repotted 

 and others not. There they remained for about 6 weeks. They were then shifted back 

 again to the cooler, north end of the house, middle bench, where they had room to grow 

 and plenty of light, but they never overcame the original crowding and stunting. This 

 interrupted growth had much to do, I suspect, with the slow progress of the disease. These 

 plants stood at first on the bench, where the very successful infections were made earlier 

 in the month of August, and the checks were close to the inoculated plants, so that they 

 were not entirely safe. 



Only a few of the affected plants were badly diseased. 



SERIES VIII AND IX, 1903. 



In 1903, at the writer's instigation, an experiment was made to determine whether the 

 disease could be communicated to field-corn and to pop-corn. This was entirely in the 

 hands of Mr. James Birch Rorer, one of my laboratory assistants, whose notes are as follows : 



