110 SCIENTIFIC REPORTS OF THfc AGRICULTURAL RESEARCH 



i 



by the First Assistant. It was found that in cases, where 

 nodule formation did not occur owing to the use of strains 

 of the radicicola organism foreign to the plant, the latter 

 nevertheless benefited by the supply of nitrogen a-symbioti- 

 cally fixed in the soil to which such organisms had been 

 added artificially. Similar results were obtained with 

 azotobacter inoculation and by the growth of legume 

 bacteria in artificial media separated from the soil contain- 

 ing the growing plant by porous cylinders. An interesting 

 and important point was noticed, namely, that in the case of 

 B. radicicola no residual nitrogen was found in the culture 

 sand suggesting that fixation of nitrogen proceeded fan 

 passu with its removal by the growing plant, whereas with 

 azotobacter this was not the case. A modified medium 

 (soil extract— mannite, — asparagin agar) was found to 

 allow ready isolation of the organisms direct from soil. 



IV. Indigo. 



The isolation of considerable quantities of pure indican 

 in the laboratory of the Indigo Research Chemist permitted 

 the use of synthetic media for the cultivation of the various 

 strains of indican hydrolyzing bacteria already isolated in 

 the Bacteriological Section during two previous seasons on 

 agar made up with indigo leaf extract. It was found that 

 very little growth or hydrolysis took place in media in 

 which indican was the only source of nitrogen, whereas the 

 addition of small quantities of leaf extract activated this 

 at once. Study of the physiological aspects of this question 

 is being carried on. 



Manufacture. Further experiments were carried out 

 in the experimental factory on the hot water extraction 

 method. Very good results were obtained by the use of 

 lime precipitation following extraction and preceding ino- 

 culation with hydrolyzing bacteria; the improvement not 

 only included higher percentage extraction of the indican 

 present in the plant, but greater purity in the product. 

 Experiments were initiated in the use of hypochlorite steri- 



