H. B. Hutchinson and N. TT. J. Miller 185 



usual method, that of simply soaking the seeds in mcrciu-ic chloride 

 solution, was found to he unsatisfactory owing to the persistence with 

 which occasional air-bubbles rt-niain on or inside the seed, and thus 

 prevent complete sterilisation. A greater amount of success was at- 

 tained by subjecting the seeds to a preliminary treatment with ether 

 or alcohol and subsequent transference to the disinfectant solution. 

 The most satisfactory results, however, were obtained by treating the 

 seeds in a warm mercuric chloride soluti(m after the removal of any 

 air-bubbles by means of a vacuinn pump; for this purpose the 

 following apparatus was used. 



Fin. 1. 



A stout-Avalled glass flask B, bearing a rubber cork with two glass 

 tubes, was attached on the one hand to a safety flask A, and on the 

 other, by means of a three-way tube, to two glass flasks of about 

 1 litre capacity G and D. C was filled with a 0"25 per cent, solution 

 of mercuric chloride, D with distilled water. The whole apparatus was 

 then sterilised in the autoclave at 125° C. for half an hour, and after 

 being allowed to cool to 40" C, the flask A was attached to a vacuum 

 pump. Seeds of approximately equal size were then placed in the 

 flask B by means of a funnel — to prevent contact between the seeds 

 and the neck of the flask — and mercuric chloride was drawn by means 

 of the pump into B from G. The connecting tube was then closed 

 with a screw-clip and B was evacuated until the solution began to boil. 

 By this means all air-bubbles present on the surface of the seed or 

 between the cotyledons and the seed-coat were withdrawn, and on 

 releasing the vacuum the disinfectant solution was able to act on all 

 portions of the seed. 



Sterilisation was allowed to proceed for 3 — 4 minutes, and after B 

 had been inverted and the disinfectant withdrawn by means of the 



