POTATO DISEASES , IJNT I907. 309 



The tub was given one rapid tilt to entirely wet the potassium 

 permanganate with the formalin and then the door was quickly 

 and tightly closed from without. The almost entire absence 

 of the odor of escaping gas while the treatment was in progress 

 indicated that the room was practically air tight. The door 

 remained closed for 24 hours and when opened the gas was 

 still so strong that it was impossible to work in the room for 

 from 20 to 30 minutes. In fact 3 weeks after the disinfection 

 was finished a distinct odor of formaldehyde could be detected 

 in the room. 



The seed for the entire 20 acres was treated in this way, 

 care being taken to place the treated seed in barrels which had 

 never been used for potatoes before. This to avoid contami- 

 nation in taking to the field after treatment. . 



To secure more accurate data than could be obtained from 

 the general results from the large field, 2 barrels of potatoes 

 were obtained which were said to be sorted from the same lot. 

 The tubers of one barrel, which are referred to as "scabby" seed, 

 were so scabby that they were absolutely unfit for market. Fig- 

 ure 46 is a fair example of these. Those of the other barrel, 

 represented by Figure 47, are referred to as "smooth" seed in the 

 following account. They were quite free from scab, although 

 frequently, as in the illustration, 1 or 2 scab spots could be 

 found on a tuber. Each barrel of seed was divided into 4 

 different lots according to treatment; care being taken not to 

 mix the smooth and scabby seed of each treatment. 



The treatment of the different lots was as follows: No. 1. 

 Soaked 2 hours in a solution containing one-half pint o_f for- 

 malin in 15 gallons of water. No. 2. Treated with formal- 

 dehyde gas as described above. No. 3. Soaked 2 hours in a 

 solution containing 20 ounces of sodium benzoate in 15 gallons 

 of water. No. 4. Untreated. Since soaking in formalin solu- 

 tion is one of the 2 standard remedies for scab, Nos. 1 and 4 

 were inserted as checks for comparison. The writer is not 

 aware that sodium benzoate used in No. 3 has been tried for 

 this purpose before, but the well-known qualities of this chem- 

 ical as an antiseptic suggested its possible value as a method 

 of treatment for potato scab. 



The crop was planted May 23, each treatment and each kind 

 of seed in each treatment being kept separate. The treated 



