Pethybridge and Murphy — Bacterial Disease of the Potato. 21 



the remaining two were stabbed in a region outside of the fiask, and exposed 

 to the suiTounding aii-. One of the control stalks was stabbed within and the 

 other outside of the flask. 



After two days the stabs on the stalks within the flasks were plainly ^-isible 

 as black marks, and there was an indication of the commencement of attack. 

 This was the case also, but to a more limited extent, with the two stabs made 

 outside the flasks, whereas in the case of the controls the woimds could only 

 be foimd with difficrdty. The signs of attack increased dur-ing the next thr-ee 

 days, by which time it was quite clear that in the case of two at least of the 

 stabs within the flasks the inoculation had " caught on." After twenty-one 

 days, one of the stalks which was stabbed outside the flask was practically 

 dead. It was spht longitudinally, and a certain amoimt of blackening, accom- 

 panied by rotting of the tissues, was found to have occurred both above and 

 below the woimd over a total distance of about one inch. After tlnr-ty-fom- 

 days one of the stalks wliich had been stabbed within the flask was fotmd to 

 be wilted, and had fallen over at a point above the place of inoculation. On 

 cutting it open, the pith was formd to have rotted away for about a total 

 distance of four inches above and below the woimd, the rot having extended 

 through two solid nodes, rendering them hollow. The ea^dty was blackened 

 and dry, without pulp, and the hidications were clearly those of an attack of 

 Black Stalk-rot. An attempt was made to recover the organism fi-om the 

 decayed tissues, but it was not successful. 



After forty-seven days a second one of the stalks which had been inocidated 

 within the flask was examined, the signs of decay being similar to, Imt less 

 extensive than, in the case just described. Here also an attempt to recover 

 the organism was attended with no success. 



After fifty-six days the thu-d and last of the stalks inoculated within the 

 flask was examined, and showed the same signs as in the pre\ious cases. The 

 attempt to recover the organism here, however, met with complete success. 

 At the same time the remaining stalk of the two which were inoculated 

 outside of the flask was examined. The signs of rot here were but meagi-e, and 

 no attempt was made to recover the organism. 



It will thus he seen that in aU five cases where the stalks were inoculated 

 with the organism a certain degree of rotting was set up, greater in some 

 cases than others, and that in one case the pathogenic organism was re-isolated 

 from the decayed tissues mth certainty. 



(h) Inoculation of plants grovjn in pots. — Much greater success was obtained 

 in this series of inoculations. Seven plants were used in the experiment, two 

 of them being used as controls — that is, being treated like the remainder as 

 regards stabbing, but the culture of the organism being withheld. In three 



