20 Proceedings of the Royal Irish Academy. 



IV. Inoculation Experiments with Living Plants. 



In this connexion two distinct series of experiments were carried out. In 

 the first, inoculations were made on single healthy potato stalks, which were 

 removed from the soil and placed with their washed lower ends (on which the 

 roots were allowed to remain) submerged in flasks partially filled with rain-water 

 kept in the lobby of the laboratory, standing in a window facing west. Tufts 

 of cotton wool placed in the necks of the flasks helped to support the stalks, 

 and prevented too rapid loss of water by evaporation. What loss there was 

 was made up occasionally by the addition of fresh water. In the second the 

 inocidations were made on plants grown for the purpose from small tubers 

 (variety " Champion "), planted in ordinary pots on May 9th. These plants, 

 although well grown, were small, and therefore were convenient for handling 

 at the time the inoculations were made. They remained out of doors the 

 whole season, and were very thoroughly sprayed twice, in order to ward off 

 the attacks of Pliytophtlwra — a very necessary precaution which successfully 

 accomplished its purpose. 



(a) Inoculation of stcdks standing in water. — For several reasons this method 

 of experiment did not prove a very satisfactory one. The time taken for the 

 organism to cause a very appreciable amount of damage to the stalks was a 

 prolonged one ; and although they remained on the whole fresh enough, they 

 were evidently not very happily situated, with their roots merely in rain- 

 water. During the period, in one or two of the flasks, a considerable growth 

 of fungus mycelium developed about the roots of the stalks, which, however, 

 did not seem to adversely affect them in any way, and which was from time 

 to time washed off. No protection was afforded to the flasks against the action 

 of light, and in all of them, towards the end of the experiment, a more or less 

 considerable growth, of a bright red unicellular alga, had accumulated, chiefly 

 on the bottoms and sides of the flasks. Nevertheless the results, as will be 

 seen, cannot be said to have been altogether unsuccessful. 



Seven flasks in all were set up as described. The inoculations made on 

 July 27th were carried out, as was pre\'iously the case with tubers, flrst by 

 stabbing into the stem with a sterile steel needle, and then introducing the 

 inoculating material on a sterile platinum wire. Two of the stalks were 

 stabbed and the platinum wire introduced into the wound without being first 

 dipped into the culture of the organism. These served as controls, and it may 

 be stated at once that throughout the experiment neither of these controls 

 showed any signs of the disease — the stabs, indeed, soon dried up, and were 

 not easily discernible. Of the other five, three stalks were inoculated in a 

 region which was within the flask, but above the water-level, so that the 

 surface of the wound was kept continuously surrounded by a moist atmosphere ; 



