778 Popular Editions oe Station Bulletins of the 



or nine volumes of oxygen. Potatoes have this power of adsorbing 

 considerable quantities of formaldehyde gas upon their surfaces, 

 until, when it reaches a certain degree of concentration, it enters 

 into a chemical combination with the tissues around a lenticel, 

 an eye or a wounded place and produces death of these tissues. If 

 the number of potatoes be small the concentration readily continues 

 until this danger point is reached and passed; but if the quantity 

 be large and the amount of surface extensive the adsorption ceases, 

 through lack of available gas to draw upon, before this point of 

 dangerous concentration is reached. This power of the potatoes to 

 adsorb formaldehyde gas and thus to reduce the amount of the 

 free gas in the air of the disinfection chamber was quite evident by 

 direct observation when attention was called to it. On opening 

 the chamber after fumigating only a few tubers, the gas was so 

 strong that it was impossible to thrust one's head within because 

 of choking and smarting the eyes, but when the quantity of tubers 

 was large and the same amount of gas was generated, so little of 

 it remained free in the air of the chamber that one could breathe it 

 without great discomfort. In the cellar fumigation, the gas was 

 still so strong in the back part of the room 16 hours after the door 

 had been opened that additional ventilation had to be provided 

 before handling the potatoes. 



By other experiments it was proven that it was adsorption, not 

 absorption or chemical union of the gas with the potatoes, that 

 withdrew it from the air; for when 5| bushels of cobblestones were 

 substituted for the same bulk of potatoes in the chamber they also 

 adsorbed the gas so that its disappearance from the air was equally 

 evident to the senses and the injury to check tubers was almost 

 equally slight. 



That injury similar to that in the Station cellar had not been 

 noted in other experimental or commercial fumigating is probably 

 due to the use of small disinfection rooms quite well filled with 

 potatoes in order to economize in the purchase of materials. In 

 the Station work economy seemed to lie in the purchase of more 

 chemicals rather than in fitting up a smaller room and moving the 

 potatoes to it. The experience, though immediately disastrous, 

 may be valuable if it serves as a warning to others not to use large 

 rooms for such disinfection unless the quantity of potatoes is also 

 large. 



This extensive series of fumigation tests gave an 

 Gas treatment excellent opportunity to learn the effectiveness of 

 not certain the gas treatment under varied conditions; and 



to destroy tubers known to be carriers of disease were included 



Rhizoctonia. in many of the tests. It would have been fortunate 



if the disease to be studied could have been scab, 

 the one for which seed treatment is most commonly used. Unluckily, 

 however, the fungus producing this disease does not grow readily 



