root-hairs, and according to the power of the organism to gain 

 access, and to establish colonies, so is the particular plant bene- 

 fitted and the stock of fixed nitrogen increased. This power of 

 the adaptability of the organism is designated its " virulence," a 

 term, however, which is perhaps hardly suited to our English mode 

 of expression, though it may for the present be retained. It has been 

 found that organisms of what is called "high-virulence" are capable 

 of entering with ease the root-hairs of vigorous plants at an early 

 stage of their growth, and of inducing the formation of nodules 

 that are large, numerous and placed high up on the roots. Or- 

 ganisms of low virulence, on the other hand, can only enter plants 

 of feebler growth, or plants that have passed the most vigorous 

 stage of youth, so that the nodules, in this case, are small and 

 scarce, and distributed, for the most part, near the ends of the 

 roots. The practical object, therefore, would appear to be the 

 breeding of strains or varieties of organisms of high virulence, 

 adapted to the symbiotic requirements of the various important 

 species of farm and garden leguminous crops. 



The nitragin put on the market a few years ago was used in 

 two ways, being either applied directly to the fields, or mixed 

 with water and brought into contact with the seed before sowing. 

 Under the former method of procedure an increase of crop was 

 obtained only when the nitrogin was used on land containing much 

 humus. The explanation given for failure under other conditions 

 was that the bacteria artificially introduced perished for want of 

 food before the leguminous seed germinated and produced plants. 



Failure of the nitrogin to effect an improvement in the crop 

 when it was sprinkled on the seed is now believed to be due to 

 the action of secretions produced by the seed in the early stages 

 of germination. These secretions are found to be rich in salts of 

 potash, and when brought into contact with the bacteria in ques- 

 tion they induce changes allied to plasmolysis, and these changes 

 are subsequently followed by death. This difficulty was found to 

 be got over by moistening the seed and allowing it to sprout before 

 the nitrogin was applied ; but manifestly such a procedure would 

 always be difficult, and often impossible, to carry out in practice. 

 The object, however, would appear to have been gained in another 

 way, namely, by cultivating the bacteria in a medium that imparts 

 to them the necessary power of resistance. Such nourishment 

 may take various forms, but that which gave the best results con- 

 sisted of a mixture of skim milk, grape sugar and pepton, and it 

 is in this medium that the organisms of the nitrogen now dis- 

 tributed are cultivated. 



Early in the present year the new nitragin was being offered 

 free of cost to all members of the German Agricultural Society on 

 the condition that it was used in accordance with the directions 

 that accompany it. In conse(|uence of the large demand the free 

 offer was in April withdrawn, but the substance may be purchased 

 from Prof. Hiltner, of Munich, in quantities sufficient to treat the 



