494 Scientific Proceedings, Royal Dublin Society. 



a small incised wound was made with a sterile scalpel at the region of soil- 

 level, and into each wound a small portion of a six-day-old pure culture of 

 the fungus was inserted. The wounds and their contents were then wrapped 

 round with a bandage of tinfoil. A third plant was "treated similarly, except 

 that no inoculating material was placed in the wound ; and this plant served 

 as a control. 



After the expiration of forty-eight hours it was clear that infection of the 

 two inoculated plants had occurred, for rotting had set in beneath the tinfoil 

 and had extended beyond it. Both plants had a tendency to fall over at the 

 point of infection, and one of them was staked in order to prevent this. 

 After a further two days the unstaked plant had fallen over and its lowest 

 leaves were beginning to turn yellow. The upper part of the plant, however, 

 was but little affected and had responded to the stimulus of gravity by carry- 

 ing out a negatively geotropic curvature. In both plants the diseased areas 

 had become shrivelled and brown, and they closely resembled naturally infected 

 plants as seen in the nursery. The control plant showed no symptoms of 

 disease throughout the experiment. These plants as seen four days after 

 inoculation are illustrated in fig. 2, PI. XLV. 



A portion of the diseased tissue of one of the plants was incubated in a 

 moist atmosphere, and the result was the production of a fair crop of sporangia 

 exactly similar to those already described as being found on naturally infected 

 plants. From the remaining portion the fungus was re-isolated by the method 

 already described, and grown in pure culture ; and it was found to be similar 

 in all respects to that used for inoculation purposes. 



This experiment clearly proved the pathogenic character of the fungus ; 

 and this has been confirmed by the results of very many inoculation experi- 

 ments, subsequently carried out, in which failure to produce the disease has 

 not once occurred. In plants which are older, infection following artificial 

 inoculation occurs more slowly, but even in such cases the fungus ultimately 

 obtains the mastery and the plants become killed. 



Successful inoculation experiments were also made with tomato fruits, 

 both green and when ripe. The fungus causes a rather rapid rot of the ripe 

 fruit, accompanied by a most offensive odour. The type of rot produced is 

 quite different from that described under the name of " Buckeye " rot by 

 Sherbakoff (13). and due to Phytophthora terrestria. In one case — the only 

 one where the attempt was made — the fungus was re-isolated in pure condi- 

 tion from an artificially rotted ripe tomato fruit, and proved to be identical 

 with that used for the inoculation. 



Infection experiments have also been carried out with various other plants. 

 Negative results were obtained with Senecio vulgaris, Helianthus annuus, and 



