770 Popuxab Ek>iTioNs of Statiom Bulletins of the 



A low temperature of the chemicals used, however, may have quite 

 an effect upon the efficiency of the fumigation, since chemical com- 

 bination is much less active at low temperatures. In one test where 

 the formalin and potassium permanganate crystals were cooled to 

 34° F. before uniting them, the reaction was a failure; but at 51° 

 the final combination was as complete as at 71°, though the release 

 of the gas was much slower. 



A high moisture content of the air in a disinfection 

 Humidity. chamber is held to be helpful in securing perfect 



results; but the humidity will probably be high 

 enough under conditions usual in fumigating potatoes; for this 

 work will ordinarily be done in a cellar or other room without 

 artificial heat to dry out the air. In none of the Station tests 

 was the humidity, when at its maximum for the test, less than 

 73 per ct. In most of the tests it reached a maximum of 90 per ct. 

 and in one the air was apparently more than saturated, the recording 

 instrument showing 104 per ct. Under these conditions, with no 

 test in air really low in humidity, it is impossible to say how much 

 increase in moisture content increases the efficiency of the gas; 

 but apparently slightly more injury resulted when the humidity 

 was high. 



Tubers wet when placed in the disinfection chamber showed con- 

 siderably more injury than those in the same test that were thor- 

 oughly dry. This point is of some practical importance; for potatoes 

 brought from a cool cellar into warm, moist air quickly become wet 

 through condensation; and if other conditions were favorable might 

 be injured by fumigation because of the moisture. 



Under almost all conditions, tubers that had just 

 Sprouted begun to sprout, that is, with sprouts an eighth of 



potatoes. an inch long or less, were much more seriously 



injured than those with dormant eyes, or even 

 those with longer sprouts. Such sprouted tubers are undoubtedly 

 really injured for seed; but it is believed that potatoes with dormant 

 eyes, and that show no eye injury within three days after treatment, 

 may still be used for seed even though somewhat spotted about the 

 lenticels. This lenticel spotting is usually least severe at the eye 

 end of the potato, as shown very plainly on the dumb-bell shaped 

 tuber illustrated on the title page. 



In tests of a dozen or more varieties, slight differ- 

 Some enccs in susceptibility were shown; but Sir Walter 

 unimportant Raleigh, the kind so severely injured in the original 

 factors. fumigation, was found no more liable to the spotting 



than several other varieties. In this first fumiga- 

 tion the tubers on the tops of the crates were most injured; but 

 in the other experiments no logical explanation for this fact could 

 be discovered. It clearly shows a stronger action of the gas on these 

 outer tubers, however, and would seem to indicate that, to secure 



