STEWART'S DISEASE OP SWEET CORN (MAIZE). 97 



The conditions following inoculation in both series were made as favorable for infection 

 as I could render them without injury to the plants, i. c, they were such as the plants would 

 be subject to in the field during wet, warm, and cloudy weather. 



The plants of Perry's Hybrid (first series) were 3 to 5 inches high and had three well- 

 developed small leaves when inoculated. Those of the Early White (first series) were 1 to 3 

 inches high when inoculated, in most cases with two leaves, but occasionally the tip of a 

 third leaf was visible, while in a number of instances only one leaf was to be seen. 



As soon as inoculated the plants of this first series were placed under the bench in obscure 

 light for nearly two days (2 to 5 p. m. August 9 to 10 a. m. August n), and the floor of the 

 greenhouse was very thoroughly wet down with water, so that the air of the house should be 

 unusually moist. 



At 10 a. m., August 10, the plants were examined. The tip of nearly every leaf bore a 

 little drop of exuded water and the conditions appeared to be very favorable for infection 

 unless it were that the excess of fluid poured out should wash away all the infectious material, 

 which may have been the case in some instances. The morning was cloudy and the temper- 

 ature 2QC.,the same as the day preceding, but probably somewhat higher in the hot-house. 



At 10 a. m., August 1 1, the pots were taken from under the bench and placed on the 

 bench. Many of the leaves still bore drops of water at their tips, especially the younger 

 ones. The plants had grown about 2 inches and the new growth was rather pale green, 

 owing to the obscurity. The earth in the pots was very wet and occasionally there was a 

 trace of mold on the surface. Roots in quite a number of the pots had come to the surface, 

 owing to the darkness. The sky was overcast and the temperature was 29 C. The gardener 

 was directed not to water the plants that day. At 2 h 3o m p. m. the temperature of the lab- 

 oratory was 31 C, the sun was shining, but there was not much wind, and the air was full 

 of moisture. 



In the second series, the first inoculation was made with cultures 24 hours old, the 

 second with cultures 48 hours old, the third with cultures 3 days old, the fourth with cul- 

 tures 4 days old. A good atomizer was used which broke the fluid into an extremely fine 

 mist or fog. The plants were small when they received the first spraying. They were 3 to 

 6 inches high when they received the fourth spraying; each spraying was made at sunset. 

 On the morning after each spraying it was observed that little beads of fluid stood on the tips 

 of many leaves (see this monograph, vol. I, fig. 73), so that here also it was judged that the 

 conditions favored infection. 



Local signs were first visible at the tips of the inoculated leaves and within a few days in 

 some cases, but there were no constitutional signs until the nineteenth day after inoculation 

 (first series) and then only in two plants. In case of the sprayed plants, 52 days intervened 

 between the last spraying and the first cases, i. e., fewer bacteria entered the plant, and a 

 longer time was requisite for infection. 



The plants of both series were removed from the hot-house to the open field on the same 

 day. They were then 18 inches to 2 feet high, healthy in appearance, and with leaves from 

 one to two inches broad. The pots were well watered before removal, and after careful 

 transplanting each hill of plants was watered and the wet earth was then covered with loose 

 earth to prevent rapid evaporation. The day was sunny and warm, but there had been 

 heavy rains the previous afternoon and evening, and the plants did not suffer from the re- 

 moval. Not a single one of them died as a result of the transplanting. 



They were set in a freshly plowed and harrowed, fertile, level field from which a crop of 

 potatoes had just been harvested. No other corn plants were near them, but at some dis- 

 tance there were several acres of healthy field corn of several varieties. The hills were set at 

 a good distance apart each way and the field was freely cultivated so that no weeds grew. 



Three additional cases appeared in the first series on September 8 (twenty-ninth day 

 after inoculation), and thereafter no more for a month. Meanwhile the plants grew vigor- 



