DISEASES OF PLANTS. 907 



In the first experiinent the limed plats had received 2J tons per acre 

 of air-slacked lime in 1893, and ^ ton additional in 1894. One lot of 

 seed tubers treated with corrosive sublimate was planted on soil that 

 had not groivn potatoes for many years. A second lot of untreated 

 tubers was planted on soil supposed to be uncontaminated, while a 

 third was planted on soil that had grown a crop of potatoes in 1893. 

 The limed plats in all 3 cases produced scabbed potatoes, while the 

 acid soils gave scabbed tubers only in 2 cases where untreated seed 

 had been used. Sugar beets grown between the rows where no pota- 

 toes had been i)reviously raised were in all cases free from scab, show- 

 ing that the disease does not spread laterally with very great rapidity. 



In the second experiment to test the value of the corrosive sublimate 

 treatment, no potatoes had been grown on the plats for at least 10 years, 

 and the application of lime was the same as in the previous experiment. 

 The authors summarize their conclusions on this experiment as follows: 



" (1) In every instance there is a greater percentage of scabbed tubers on the limed 

 than on the unlimed sections where the seed tubers were not previously treated with 

 corrosive sublimate solution. 



" (2) The treatment with corrosive sublimate solution appears to have unquestion- 

 ably reduced the percentage of scab upon the limed sections. 



" (3) In case of the unlimed sections, there was in one instance a greater percent- 

 age of scab where the seed tubers received the corrosive sublimate treatment, while 

 in the three other instances the per cent of scab was less. These results are contra- 

 dictory in two instances, and in the other two the differences are so slight that as a 

 whole no practical advantage from the treatment is apparent. 



" (4) It will be seen that without exception some scab resulted on both limed and 

 unlimed sections of the plat, even when the corrosive sublimate treatment of the 

 seed tubers was employed. Bearing in mind that beets, grown in another place upon 

 soil known to have been previously contaminated with the germs of the dise:iae, 

 were badly scabbed, and in consideration of the fact that beets have in no other 

 instance been found to be scabbed when grown on any of the plats in the vicinity, 

 we have striking circumstantial evidence from the scab upon the tubers grown from 

 treated 'seed' that they probably owed their diseased condition to the introduction 

 of undestroyed germs on the seed tubers and not to the preexistence of the germs 

 in the soil itself." 



In the third experiment the primary result was not a study of potato 

 scab, but the tabulated results show a tendency of lime to increase the 

 potato scab. 



In the pot experiments the object was to test the effect of different 

 forms of lime on scab development. It is claimed that wherever lime 

 in the form of carbonate or in forms capable of producing carbonates 

 was used the per cent of scab was increased. Sulphate of lime gave 

 conflicting results. Calcium chlorid gave least scab, but it injured 

 the growth of the potatoes. No attempt is made to draw definite 

 conclusions from this series of experiments. 



The authors conclude as follows : 



" Experiments with air-slacked lime covering a period of 2 years show conclusively 

 that it tends to increase the scab of potatoes. 



