April IS. X9I9 5"^^^ Disinfection by Formaldehyde Vapor 37 



used above were placed in a series of sterile petri dishes, two sets of each 

 kind of seeds being used. One set of dishes was held untreated as a 

 check and the other set was given the vapor, using formaldehyde solution 

 at the rate of 20 ounces per 1,000 cubic feet for 2 hours. The plates 

 were all poured in the usual way and observations were made for several 

 days. This experiment was repeated three times, and very promising 

 results were secured. Alfalfa, carrot, clover, field pea, flax, lettuce, 

 millet, muskmelon, radish, and soy beans were free from fungi when 

 treated, but fungi were present in abundance in all the checks, except 

 flax. 



In practically all cases, whether treated or untreated, a few bacteria 

 developed on the plates, but the treated plates showed very few colonies, 

 while the checks showed a great many. 



In the case of barley, oats, corn, rye, rice, and wheat no growth 

 appeared for two or three days in the treated plates, while the untreated 

 plates had an abundance of growth within a day or two. This difference 

 may be due to an inhibiting effect on the part of the vapor, but it seems 

 more probable that it is due to the fact that the surface spores and 

 mycelia were killed in the case of the treated seeds and that the appear- 

 ance of fungi a day or two later is due to the growth of mycelium from 

 within. The fungi appearing in such cases were species of Fusarium and 

 Altemaria. 



It seemed desirable to determine in so far as possible what fungi are 

 present on the seeds passing through the inspection house and at the 

 same time get some additional information as to what effect the vapor 

 treatment would have on these organisms under actual working condi- 

 tions. A chance was also afforded to study the effect of the vapor treat- 

 ment, in a very limited way, on germination. 



In this work five seeds of the material to be tested were removed 

 before treatment and five after treatment. These seeds were placed in 

 sterile petri dishes and treated in the usual way. The plants were under 

 observation for several days. Bean seeds were used more than any other, 

 inasmuch as a large number of shipments of beans happened to be 

 coming in from South America. 



Out of the 86 different samples of beans treated and studied 9 seemed 

 to be retarded from one to two days in germination, while 8 were accel- 

 erated slightly, but in no case was there any apparent injury. The 

 remainder of the samples did not seem to be affected one way or the 

 other, so far as their germination was concerned. There was very 

 marked reduction in the number of fungi and bacteria present in the 

 treated samples as compared with the untreated. In taking samples of 

 this kind, average seeds were selected, and as a result some of the beans 

 were diseased and probably had internal mycelium, as in the case of 

 CoUetotrichura, thus making it impossible to render them absolutely free 

 from fungi without killing them. 



