[Vol. 10 



26 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



become affected with the disease. Only one trial was made, and 

 while the results obtained do not in themselves warrant drawing 

 a conclusion, they are of interest when compared with those re- 

 ported by Shapovalov and Edson ('21). Ordinary seed pieces 

 from sound, hard, healthy potatoes were planted in soil which 

 had been previously heavily seeded with the blackleg germ by 

 planting with tubers affected with the disease. The seed pieces 

 sprouted and the plants therefrom grew to be of good size. No 

 signs of infection by the blackleg germ were to be found in the 



seed niece, on the 



METHODS AND MEDIA 



Certain of the bacteriological methods recommended by the 

 American Public Health Association ('12) were followed as 

 closely as possible by the writer in the prosecution of his 

 studies of the cultural characteristics and physiology of the 

 blackleg strains selected for comparison. In some cases this was 

 not practicable or even possible on account of the fact that 

 certain reagents were not available, due to conditions brought 

 on by the World War. For this reason, a rather complete 

 statement is given below of the media and methods em- 

 ployed, thus making it possible to duplicate both. 



The present-day methods for determining H-ion concentra- 

 tion of bacteriological media were not in general use at the time 

 the writer carried out his comparative studies. The ordinary 

 media used were titrated with N/20 NaOH, using phenolphtha- 

 lein as an indicator. In most cases the reaction of the medium 

 was not adjusted. Wherever stated the reaction is given as "+ 

 7" etc., where the addition of 7 cc. of normal alkali per 1000 cc. 

 would render the medium neutral to phenolphthalein. A "0" 

 indicated that the medium as used was neutral to phenolphtha- 

 lein. The precaution of having all flasks, beakers, test-tubes, etc. 

 thoroughly clean was taken at all times. 



Media. — Steps in the preparation of the media are briefly in- 

 dicated below: 



NUTRIENT BROTH 



(1) To 1000 cc. distilled water add 50 gms. "Bacto" Beef Ex- 

 tract; (2) heat the mixture gradually up to 70°C. during about 

 1 hour; (3 ) boil for a few minutes to coagulate precipitable proteins; 

 (4) make up the water lost by evaporation; (5) filter through layers 

 of clean cheese-cloth; (6) cool to about 60 °C. and add 1 per cent 

 Difco" peptone, Va P er cent NaCl, and dissolve; (7) filter through 



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