SEED STERILIZATION AND ITS EFFECT UPON INOCULATION. 7 



From Table IV it appears that the sterilizing agents which are 

 least able to pass through the seed coat into the seed were more 

 nearly removed by the scant washing than those which could pene- 

 trate to the interior of the seed. 



Hutchinson and Miller" have shown in an ingenious way that the 

 persistence with which air bubbles remain on or inside the seed is 

 responsible in many cases for incomplete sterilization. The use of a 

 vacuum pump in connection with seed disinfection gave satisfactory, 

 though not perfect, results. 



As a means of sterilizing legume seed, this method seemed promis- 

 ing, but presented the possibility that there might be increased diffi- 

 culty in freeing the seed from traces of the disinfectant. Accord- 

 ingly, a test of the method was made, barley being used in addition 

 to tile seeds of several legumes in order to test further the semi- 

 permeable character claimed for the barley seed coat. It Avould 

 naturally follow that poisons which penetrate the seed coats would be 

 less completely removed by rinsing than those which are excluded by 

 selective action. 



Fifty seeds each of peas, beans, vetch, and barley selected for uni- 

 formity were treated by the vacuum method, and a like series by the 

 usual method, shaking the seed up with the disinfectant in flasks. 

 Each lot was rinsed four times, the last wash water (after standing 

 fifteen minutes on the seed) being saved. This final wash water was 

 then inoculated with Bacillus suhtUis and allowed to stand two days, 

 and platings Avere then made on beef agar. Counts made on these 

 plates two days later indicated the toxic effect of the disinfectant left 

 on the seed after rinsing. The seeds were germinated in sterile petri 

 dishes by pouring into the dishes sterilized melted agar. An ex- 

 amination of the petri dishes one week later showed whether the seed 

 had remained sterile or not. 



No comparisons were made as to germination, except that a note 

 was made when it appeared that the treatments had killed or injured 

 the seed. Hydrogen peroxid (3 per cent), sulphuric acid (25 per 

 cent), and mercuric chlorid (0.5 -per cent) were selected for the dis- 

 infectants to be used, each lot of seed being treated for five minutes. 

 In the vacuum series each solution was warmed to 40 to 50 degrees 

 Centigrade, so that when a vacuum was applied the solution would 

 boil. Air was admitted after a very brief boiling, and the solution 

 allowed to act for five minutes. By connecting four bottles in series 

 it was possible to draw off the disinfectant and to introduce the 

 sterile wash water without opening the bottles. The results are given 

 in TabU' V. 



".Journal of Agricultural Science, vol. 3, pt. 2, October, 19()9, p. 170. 

 [Cir. 07] 



