TO June. 1910.] Experiments 7i'itJi Potato Diseases, igog-io. 361 



With reference to the wart-like excrescences or galls on the tubers, it 

 IS believed bv growers that they are due to rain, after a long dry period, 

 which causes the formation of blisters. This may be partly true, but never- 

 theless the appearance is the result of the presence of the Potato Eel -worm, 

 W'hich lies in a desiccated state in the dry soil, and only becomes active 

 after a fall of rain. 



The accompanying illustration of an affected tuber will show what takes 

 ]>lace under the influence of abundant soil moisture due to^ a fall of rain. 

 The field from which it was taken was carefully inspected on 26th January, 

 The tubers then showed no sign oi eel-worm, but on 6th March and 

 following days upwards of 2 inches of rain fell. The plot was visited 

 again on 31st March, when it was found that manv of the tubers had 

 made a second growth and many entirely new tubers had been formed. In 

 every instance these, as well as the new growth on the old tuber, had been 

 attacked. The left hand or clean portion shows the stem end on oldest 

 part of tuber, the right hand the new. If the weather conchtions had not 

 favoured the development of the worms before the tubers had become firm 

 in the skin, the crop would have escaped the attack. 



A. — Eel-worm. 



In this experiment, two pots containing sterilized soil were used. 

 In Xo. I a clean Carman tuber which had been dipped in formalin solu- 

 tion (i lb. to 30 gallons of water) for two hours was planted, whilst in 

 pot No. 2 another Carman tuber, treated in a similar manner, was planted. 

 To the second pot was added a further tuber of the same variety, from 

 which all the eyes were removed to prevent it growing. Thi.s was covered 

 with eel-worm galls. 



When harvested on 2nd March, no galls had been formed on any of 

 the tubers produced by the plants in either pots, and both appeared clean ; 

 but on examination Mr. Laidlaw, Micro-Biologist, reported that he had 

 found worms in the abrasions of the skin of the tuber and also in the soil 

 of pot Xo. 2, whilst both the soil and tubers of Xo. i were clean. 



As the weather had been very dry up to the time of harvesting, there 

 is little doubt but that the worms had not developed before the tubers 

 became firm in the skins. 



B. — Treatment of Seed Tubers with Formalin. 



This experiment was designed to test the effect of dipping scabby seed 

 in formalin. Two very scabby tubers (Carman) were cut into two sections, 

 each making four sets. One section from each tuber was dipped in 

 formalin (i lb. to 40 gallons of water) for two hours. It was thought 

 the dipping might possiblv injure the cut sets, but such was not the case. 

 Careful notes were taken and the only difference observed was that the 

 germination of the dipped sets was retarded. Thev did not come through 

 the around for more than a week after the untreated, and the growth was 

 slow" for nearlv six weeks; then they overtook the others, and as 



