96 BACTERIA IN RELATION TO PLANT DISEASES. 



example, on July 1 6, at Mr. Croucher's, stem-segments 5 or 6 inches long and 0.5 to o. 75 inch in diameter 

 were cut from the middle part of 8 typically diseased sweet-corn plants and carried to New York, 

 where, through the courtesy of the pathologist, Dr. James Ewing, I had opportunity to examine them 

 the next day under proper bacteriological conditions in a laboratory of the Cornell University Medical 

 School. The male inflorescence was drying out in these 8 plants, but the stems were green and normal 

 in external appearance and each plant still bore some green leaves or at least green leaf-sheaths. The 

 yellow slime oozed abundantly from the vascular system when the stems were cut. By direct transfer, 

 without the intervention of poured plates, a pure culture of Bacterium stewarti was obtained from each 

 one of these 8 stems. All that was done was to work rapidly, in a clean room, in still air, and to ex- 

 clude surface bacteria by fire. The very simple steps in the process were as follows: (i) The stem 

 was rolled over and over several times in a Bunsen flame until its surface was judged to be sterile or 

 nearly so ; (2) it was then shortened an inch at one end (in the flamed part) with a butcher-knife heated 

 nearly red hot and used hot; (3) after some minutes the yellow bacteria oozed from the cut surface of 

 some of the bundles and often I hastened this oozing by squeezing the stem; (4) one or more, usually 

 several, of these droplets were touched with a sterile platinum needle which was then thrust several 

 times into the agar. The organism grew promptly and each one of the eight tubes turned out to be a 

 pure culture of Bad. stewarti. Plate-cultures were made from some of them and all remained under 

 observation more than a year during which time none of them became contaminated. Descendants 

 of these agar-stab cultures furnished the material used for making the inoculations, after I had satis- 

 fied myself by culture on various media that this was actually the same organism as that formerly 

 received by me from Mr. Stewart and subsequently lost through inattention. It should" also be noted 

 here that stabs made from the bright yellow slime and the pale yellow slime yielded cultures which 

 could not be distinguished. 



Cover-glass smear-preparations, stained with Loeffler's alkaline methylene blue and with Ziehl's 

 carbol fuchsin, were also made from each of these 8 stems (figs. 43, 44), after which they were sectioned 

 and put into 95 per cent alcohol for subsequent study. 



It is a remarkably interesting fact that 8 different maize plants should have yielded the same 

 organism in pure culture by direct transfer, but it does not stand alone (see Cobb's Disease of Sugar- 

 cane, pp. 12, 25, and Wilt of Cucurbits, vol. II of this monograph, p. 287). 



INOCULATION EXPERIMENTS. 

 SERIES 1 AND II. 1902. 



Two series of inoculations were made in August 1902, at nearly the same time. The 

 experiments did not get under way until late in the season owing to the interference of other 

 work, and they were consequently cut short by frost, but they continued long enough to 

 yield conclusive results. 



First Scries. 



This embraced two kinds of sweet corn, viz, Perry's Hybrid and Early White. The principal 

 dates were as follows: 



August 2. -Planted Perry's Hybrid. 

 A ugust 4. Planted Early White. 



A ugust Q, 5 p. m. Inoculated each sort by placing on the tips of the leaves by means of the platinum wire a small quan- 

 tity of the bacteria from young (48-hour) cultures on slant agar. 

 A ugust IQ. Shifted to 6-inch pots. 

 August 28. First cases (two). 



A ugust 28. -Transplanted from the hot-house to the field. 



September 8. Growing well and as large again as when transplanted. Three additional cases, 

 October 7. More cases. 

 October 10 to 27. -Numerous cases. 

 October 29. First hard frost. 

 November I. Closed experiment. 



Second Series. 



This embraced three kinds of sweet corn, viz, Perry's Hybrid, Early Red Cory, Early White 

 Cory. The principal dates were as follows : 



August 7. Planted. 



August 13, 14, IS, 16. The plants were inoculated at sundown on each of four days by spraying upon them in the 



form of a very fine mist aportion of soc.c. of sterile water, containing each time the slime from two young slant 



agar cultures. 



A ugust 2#. Transplanted from the hot-house to the field. 

 September S.-^-Growing well; twice as large as when transplanted. 

 October 7. First cases. 

 October 10 to 27. Many cases. 

 October 29. First hard frost. 

 November I. Experiment closed. 



