6 SEED STERILIZATION AND ITS EFFECT UPON INOCULATION. 



Table III. — Gruicth. of BuviUu^ suhtilis In rinse ivater after disinfection of seed. 



It is evident that two rinsings were not sufficient to remove the 

 hydrogen peroxid from the seed, and this part of the experiment 

 was repeated, witli one additional rinsing, giving the results indi- 

 cated in the last two lines of the table. The third wash water shoAved 

 slight inhibition in the growth of BaciUiis subtilis^ but nothing like 

 as severe checking as with formaldehyde or mercuric chlorid. 



The whole experiment was then repeated, flasks being used instead 

 of test tubes. Bean seeds, fifty to each flask, were used. Each lot 

 was rinsed three times and allowed to stand in sterile water fifteen 

 minutes between rinsings. The flasks permitted the use of about five 

 times as much w^ater for rinsing as could be used in the test tubes, 

 and the results showed practically complete removal of the disin- 

 fectants, at least in quantities toxic to Bacillus subtilis. 



Brown " has shown that the seed coats of barley have the property 

 of selective action in admitting or excluding various substances used 

 for sterilization, e. g., sulphuric acid and copper sulphate are unable 

 to diffuse into barley seed while mercuric chlorid penetrates readily. 

 Acting on this suggestion, barley seeds (fifty in each lot, uniform in 

 size and appearance and showing absence of external injury) Avere 

 treated in test tubes for one hour and w%ashed Avith sterile distilled 

 water. The fourth wash water was then inoculated Avith Bacillus 

 subtilis. Platings made tAvo days later on beef agar ga\'e the follow- 

 ing results : 



Table IV. — Residual effect of disinfcclantu on harleii seed. 



Treatment. 



Sterile water 



Sulphuric a(!id . . . 

 Copper sulphate . 

 Mercuric chlorid. 

 Formaldehyde. . - 



fecteat. I ■"-e^^-"'- 



Per cent. 



25. 



10.0 



.5 



1.0 



Aiimb) r. 



10,000 



50 



250 











"Proceedings of the Royal Society (London), vol. 81, ser. B, no. B-546, 1900, p. 82. 

 [Cir. 67] 



