MICHIGAN ACADEMY OF SCIENCE. 79 



CAN SEEDS BE STERILIZED? 



RICHARD DE ZEEUW. 



The work laid out in this study was to test the action of the follow- 

 ing agents: cleaning fluid,^ mercui'ic chloride, potassium dichromate, and 

 formaldehyde gas, on each of the following seeds: Lupine, Pea, Wheat, 

 Corn and Mustard. 



The work can be conveniently divided into two parts. The first part 

 has to do mainly with the seeds, the second mainly with the fungi and 

 bacteria. 



The first thing to be done is to determine the highest concentration 

 and the longest period of exposure in each case which will still permit 

 one to obtain a fair percentage of normal seedlings, leaving out of 

 consideration for the time being the effect of the disinfectant on the 

 adhering fungi and bacteria. A great deal of unnecessaiw and tedious 

 work would be involved in determining the effect of the disinfectant on 

 the fungi and bacteria adhering to the seeds while determining its effect 

 on the germination of the seeds. The germination tests were carried 

 on during the early fall when the laboratory had a normal temperature 

 day and night of 22^ C. This temperature was fairly constant. Lots of 

 twenty-five seeds each were exposed for different lengths of time to 

 different concentrations of eacli of the disinfectants, and after thorough 

 washing were placed in a Geneva germinator kept at room temperature. 

 They were left for four or five days and then were comi)ared with the 

 controls. These controls were treated as nearly as possible in a man- 

 ner similar to the experimental seeds, except that no disinfectant was 

 used. 



After the highest point of both exposure and concentration had been 

 determined for each kind of seeds in the different disinfectants, each 

 kind of seeds thus treated Avas then tested to determine whether bac- 

 teria and fungi could endure this treatment as well as the seeds. For 

 determining the latter point, an apparatus was constructed,, the idea 

 for which was obtained from Kehler's ('04) paper. It differs from 

 Kehler's apparatus in that the seeds, after they are once placed in the 

 disinfectant, are not exposed to contamination in any form till after a 

 two weeks incubation. Kehler transferred his seeds by means of sterile 

 forceps from the vessel in which they had been treated to the flask 

 of culture medium. 



The apparatus (see plate) is constructed as follows: There is a large 

 flask, A, which contains distilled water and is connected with a three- 

 arm glass cock. B. Flask A also has a glass tube, a, with a flange 

 worked on the end. This tube projects into the flask through the rub- 

 ber stopper. Over the flanged end of the tube is securely fastened a 

 cap of cotton, b, to filter the air as it enters the flask when the water 

 is drawn out of the flask. To the tube on the opposite side of cock, B, 

 is attached a small flask. C. This flask has also an upright flanged tul)e, 



'Cleaning fluid equals H2 SO4 sp. gr. 1.83 saturated with K2 Cr2 O7. 



