112 BACTERIA IN RELATION TO PLANT DISEASES. 



July 8, 1903. Set out to-day on the Flats 10 rows of corn, each hill containing 4 plants. The rows run from east 

 to west and are as follows, beginning at the north end of the plot: 



i. Uninoculated : 2. Inoculated (June 20 and 23) by touching water from 



Nelson's Yellow field (yellow flint) 12 hills. water-pores with loop of pure culture of Bad. steward: 



Mottled Pearl pop-corn 12 hills. Nelson's Yellow field 16 hills. 



Hominy (white flint) 12 hills. Mottled Pearl pop-corn 18 hills. 



Boone County White (white dent) 12 hills. Improved Clairage 18 hills. 



Improved Clairage (yellow dent) 12 hills. Boone County White 18 hills. 



Hominy 18 hills. 



September 30, 1903. Cut out all of the Nelson's Yellow field corn, both inoculated and uninoculated. All the 

 plants are more or less dead. The tassels are dried up and the leaves brown. There are some good ears. Many 

 stems in both lots show an abundance of yellow ooze from the bundles. A section from each stem has been put into 

 alcohol for future examination. This variety seems to be a much faster grower than any of the other varieties, which 

 as yet are quite green and the ears are not yet ripe. Could it be the disease that hastened the ripening or is it a varietal 

 characteristic? 



Only one of the five varieties proved susceptible to this disease, viz, Nelson's Yellow 

 field corn. Why were the control plants of this variety also attacked ? On making inquiries 

 I learned certain facts which appear to answer this question sufficiently. When the inocu- 

 lations were made the check-plants stood some 30 feet away, but after a few days it became 

 necessary to move the plants into another hot-house, where there was not much spare room, 

 and where the inoculated and uninoculated plants stood much crowded and close together 

 for a number of days. The infection of the check-plants probably dates from this time, as 

 the gardener's hose would spatter all of the plants indiscriminately and that would dis- 

 tribute over the control plants any bacteria remaining on the surface of the inoculated 

 ones, or on the soil of the pots. 



The cultures used for inoculating were derived (June 19) directly from those direct 

 transfers made by the writer on July 17, 1902, the organism being alive in each one of these 

 8 tubes. 



The Mottled Pearl pop-corn, Boone County White, and Improved Clairage were 

 planted June 15 and were inoculated June 20. Inoculations were made from slant agar- 

 cultures. A loop of the organism was touched to each drop of water exuding from the 

 water-pores situated on the tips of the leaves. The drop became clouded. At this time 

 the first leaf was just beginning to uncurl, so that the tip of the second leaf was exposed. 



The inoculated plants were put under the east bench in the pineapple house, where 

 they remained from Saturday afternoon until Monday morning. They were covered with 

 a framework of netting to keep out mice, and the top of this was covered with manila paper. 

 The temperature of the house went up to 41 C. on Sunday and was down to 20 C. during 

 the night. When the plants were taken from under the bench and put in the light the 

 margins of the leaves were covered with drops of exuded water and all the leaves were some- 

 what bleached. 



The White Hominy and Nelson's Yellow field corn were planted June 17 and inoculated 

 June 23, when the plants were from 2 to 4 inches high. In most of them one leaf was 

 uncurled, so that the tips of the second and third leaves were often exposed, and three leaves 

 were inoculated on some plants. The work was done in the afternoon, in the same manner 

 as in the preceding series, except that the White Hominy was inoculated from a 24-hour-old 

 bouillon-culture derived from the slant agar; the plants were placed under the bench until 

 the morning of June 25, when they were uncovered and placed on the bench. The leaves 

 were more or less etiolated. 



The result of this experiment shows that the organism had not lost its virulence for 

 susceptible varieties (Nelson's field corn) at the end of 1 1 months' growth on agar. The 

 thoroughness with which the work was done also indicates that the other varieties experi- 

 mented with are not susceptible to this disease. 



SERIES X. 1905. 



In the spring of 1905 the inoculation experiments were repeated on several varieties 

 of sweet corn and field corn grown for the purpose in a bed in one of our hot-houses. The 



