STEWART'S DISEASE OF SWEET CORN (MAIZE). 1 27 



One very badly diseased: Husks and cob included. 



One slightly diseased: 3 or 4 bundles show yellow ooze and four are browned. 

 Two badly diseased: Cobs infected. Hundreds of little yellow spots on the husks. 

 One diseased: About 20 or 30 bundles infected at base. 

 One badly diseased: No ears. 



One badly diseased: The husks as well as the stem. The leaf-sheaths show bright yellow bacterial ooze on their 

 inner surface. 



(4) Selected, bad seed, untreated (six rows) : 



Number of healthy plants, 284; number of diseased plants, 29. 

 Total, 313; per cent diseased, 9.3. 



Remarks. No notes on the first 25, some of which were badly diseased. The twenty-sixth, 

 twenty-seventh, and twenty-eighth were slightly diseased. In the twenty-ninth four bundles were 

 observed to be infected. 



GENERAL REMARKS ON SERIES XVI TO XIX. 



July 28. The germinated plants are 1 to 2 inches high. The best germinations are 

 in the plot treated with mercuric chloride 1 : 1000 for 10 minutes. The next best are those 

 treated in the same way 15 minutes. The untreated ones (unselected seed) are decidedly 

 poorer. The poorest plot is that planted with the selected bad seed. 



October g. The experiment gave about 8 times as many cases on the untreated as on 

 the treated. The contrast in the amount of infection in individual plants on the untreated 

 plots and on those treated was very striking. Many stems of the former had nearly every 

 bundle occupied to the top of the plant, and also many ears involved, and all of the leaves 

 were dried out, whereas in the latter there were only a very few plants which showed any 

 infected bundles except near the base of the plant, and most of the leaves were yet green. 

 The total bacterial multiplication in the plants grown from unsterilized seed was several 

 thousand times as much as in those grown from the sterilized seed. 



The infection of the ears was as abundant and striking in this experiment (untreated 

 plots) as in any I have ever made. Several of these ears were put into alcohol. They had 

 a very large number of yellow spots on the husks (fig. 53) and the bacterial slime had oozed 

 from some of them and was sticky to the touch. In one it was so viscid that the slime was 

 stretched out a distance of 31 inches before the cobwebby thread ruptured. 



In the untreated plots I did not find a single row that had no diseased plants in it. 



This experiment indicates to me quite clearly that the seed corn was the carrier of 

 this disease. Probably if I had extended the soaking in mercuric chloride to 20 minutes, 

 the check plots would have been entirely free from the disease instead of nearly free. I 

 feared to do this lest I might destroy the germinating power of the corn. The soil was the 

 same, the corn was the same, the water was the same, the experiment was controlled in 

 the hothouse, and the only known variable factor was the germicide. Moreover, the corn 

 was already under suspicion because of its source and of its behavior at Falls Church, 

 Virginia. 



The experiment serves to establish more firmly the conclusion drawn from an earlier 

 experiment respecting the existence of infected fields at Wakeman, Ohio. It further empha- 

 sizes the wrong done by seedsmen to the general public in selling corn grown on fields 

 infected by this organism, since it serves to distribute the disease broadcast over the country. 

 Wherever such corn is planted it not only gives a poor crop, but also serves to cause disease 

 in a succession of crops on the same land as a result of soil infection. 



The time between planting and the first appearance of cases was about 60 days. 



The plants were crowded in the rows much like fodder corn and grew spindling, many 

 of the stems being brittle. Had the plants grown uncrowded in a moist field the number 

 of cases would undoubtedly have been tripled or quadrupled, as a rapid watery growth 

 greatly favors the multiplication of the bacteria inside the stems, whereas stunted, hard 

 basal nodes often prevent the organism from getting out of the base of the plant. Probably 

 a spring planting would also have given more cases than the midsummer planting, since 

 the dried-out bacteria gradually perish with lapse of time. 



