American Experiments 233 



German method of Nobbe and his associates. The 

 German nitragin supplied to the purchaser a mass of 

 gelatin, the surface of which was covered with a growth 

 of nodule-bacteria. The number of the latter was so 

 great that their mere distribution in a quantity of water 

 and the moistening of the seed with the latter was suf- 

 ficient to allow every seed to be supplied with a number 

 of organisms^. 



The so-called cotton cultures of the Department of 

 Agriculture consisted of a piece of absorbent cotton 

 that had been moistened with a liquid culture of the 

 nodule-bacteria, and subsequently dried. The dried 

 cotton was, therefore, supposed to contain a compara- 

 tively small number of nodule-bacteria, capable of grow- 

 ing and multiplying when placed in the proper nutrient 

 solution. In order to supply the latter, the package of 

 inoculated cotton was accompanied by weighed quanti- 

 ties of cane-sugar, phosphate of potash, sulfate of 

 magnesia, and phosphate of ammonia. These salts were 

 to be dissolved in water, furnishing a complete food 

 for the nodule-bacteria, and the cotton was to be placed 

 in the solution. With conditions favorable for their 

 development, the nodule-bacteria could thus rapidly 

 increase in numbers, and could furnish sufficient ma- 

 terial for the inoculation of a considerable quantity of 

 seed. 



In the cotton method, as can be seen, the prepara- 

 tion of the cultures was really left to the farmer. The 

 danger was always present that the bacteria, molds, 

 and yeasts introduced from the air, or contained in the 

 utensils or water might prove a serious menace to the 



