Sept. 1894.] EXPERIMENTS IN CHECKING POTATO DISEASE. 



15 



the tubers in the treated plots were still adhering to the fibrous 

 roots ; the haulm on the untreated plots was generally quite 

 withered and dried up, on the plots which had been dressed 

 once only it was almost in the same conditioD, but on the plots 

 which had been twice dressed the haulm was still green and 

 succulent, though the leaves had withered away. On all the 

 treated plots there was a notable absence of weeds as compared 

 with those untreated, due to the greater luxuriance and continu- 

 ation of growth of the haulms and foliage on the treated plots 

 choking out the weeds, while the untreated haulms having died off 

 early in the season allowed the weeds to have their own way. 



There were nine complete series of experiments, in each of 

 which there were eight treated plots or 72 treated plots in all, 

 86 of which were sprayed with a 2 per cent, mixture, and 36 

 with a 1 1 per cent, mixture. 



A comparison of the results obtained in those plots which were 

 similarly treated with respect to the method and frequency of 

 application, but which varied with respect to the per-centage of 

 copper sulphate contained in the mixture applied, indicates that 

 the best results were obtained with a 2 per cent, mixture in 21 

 cases, and with a IJ per cent, mixture in 15 cases. 



The plots which gave the highest value in yield in each of 

 the nine sets of experiments had been dressed, in six instances, 

 with a 2 per cent, mixture, and, in three instances, with a 1^ per 

 cent, mixture. 



Comparing the results obtained in each set of experiments by 

 the different systems of application adopted, irrespective of the 

 per-centage of copper sulphate contained in the mixture, it 

 appears that the plots giving the highest yield in value in each 

 set of experiments were dressed in two instances from above 

 and below on one date only, in one instance from above only, 

 and in six instances from below only, the dressings in these 

 last seven cases having been applied on two separate occasions 

 at intervals of about four weeks. 



A comparison of the average returns per acre of those plots 

 which received similar treatment in each series of experiments 

 shows that the plots which were sprayed from above and from 

 below, on two distinct occasions, gave the best average returns. 



Comparing the mean results obtained on those plots in each 

 set of experiments, which were treated similarly as to the 

 method of dressing, and number of dressings given, but one of 

 which was dressed with a 1^ per cent, mixture, and the other 

 with a 2 per cent, mixture, it appears that on the duplicate- plots, 

 giving the highest mean yield in value, the dressing was applied 

 from above and below in one instance on one date only, and in 

 two instances on two separate occasions at intervals of about 

 four weeks, while in two instances it was applied from above 

 only, and in four instances from below only. 



It would appear, therefore, that in the case of the Champion 

 variety of potatoes it is desirable to use a mixture containing 



