212 Report of the Department of Botany of the 



tubers have been long in storage. It occurred to us that such 

 development of the lenticels might make the tubers more liable to 

 gas injury, but we could find no evidence that such is the case. 



It has been established that the quantity of formaldehyde gas 

 evolved varies somewhat according to the proportions in which the 

 chemicals are mixed. Several investigators have attempted to 

 determine the most economical ratio of permanganate to formal- 

 dehyde, but if we are to judge by the recommendations of state 

 boards of health in the United States they have not succeeded in 

 fully solving the problem. Several different formulas are in use. 

 But this is not a factor in our present problem because the propor- 

 tions used at the time of our disastrous experience with the gas 

 treatment, also in nearly all of our experiments, were those used 

 by Morse in his experiments, viz., .475 gram of permanganate to 

 each cubic centimeter of formaldehyde solution, which is the ratio 

 recommended by Evans. 39 



Since our experiments have shown that the quantity of potatoes 

 per cubic foot is a factor of prime importance the question naturally 

 arises as to the advisability of varying the quantity of formaldehyde 

 according to the quantity of potatoes. Undoubtedly, this must be 

 done if uniform results are to be obtained, but the few experiments 

 which we have made do not warrant us in making recommendations 

 as to just how it should be done. In three of our experiments 

 (Nos. 18, 24 and 78) the standard quantity of formaldehyde was 

 doubled and in two others (Nos. 17 and 21) it was halved. (See 

 Table II.) The tuber injury in Experiment No. 78, in which four 

 pounds per cubic foot were treated with double the standard dose, 

 was practically the same as in Experiments 79 and 83 in which half 

 this quantity (2 lbs. per cubic foot) were treated with the standard 

 dose. 



In room disinfection 3 or 4 hours' exposure is usually deemed 

 sufficient. In three of our experiments (Nos. 68, 69 and 71, 

 Table II) the length of exposure was only three hours. The amount 

 of tuber injury was appreciably less than in comparable experiments 

 in which the exposure was 24 hours. 



™Loc. tit. 



