Bacteria and, the Ni troy an Problem. 521 



creased from five to ten times that which usually occurs in nature. 

 Practical field experiments have shown that of two cultures, one 

 grown on nitrogen-free media and the other on a medium rich in 

 nitrates, the first will produce abundant tubercles, while the latter 

 will be absolutely worthless and fail to produce a single nodule. 



Distribution and Methods of Use of Cultures- 

 Having secured an organism which was able to fix such a large 

 amount of nitrogen, it was necessary to devise some means of pre- 

 venting this property from being lost, as well as to enable the cultures 

 to be distributed in sufficient quantity to be of some practical use. It 

 is now known that the bacteria, when grown upon nitrogen-free 

 media, will retain their high activity if they are carefully dried out 

 and then revived in a liquid medium at the end of varying lengths of 

 time. By using some absorbent which will soak up millions of the 

 tubercle-forming organisims and then by allowing these cultures to 

 become dry the bacteria can be sent to any part of the United States, 

 or the world for that matter, and yet arrive in perfect condition.* Of 

 course, it is necessary to revive the dry germs by immersion in water, 

 and with the addition of certain nutrient salts the original number of 

 bacteria is greatly increased if allowed to stand for a short time. 

 Frequently twenty-four hours are sufiicient to cause the water in a 

 pail to turn milky white with the number of organisims formed in 

 that time. Thus, by sending out a dry culture, similar to a yeast 

 cake and no larger in size, the original number of nitrogen-fixing 

 bacteria may be multiplied sufficiently to inoculate at least an acre of 

 land. The amount of material thus obtained is limited only by the 

 quantity of the nutrient water solution used in increasing the germs. 

 It is evident, therefore, that the cost of inoculating land is very small. 

 The principal cost is in obtaining the organisms, but the methods 

 perfected by the Department of Agriculture now make it possible to 

 produce these at a comparatively small cost. Special facilities for 

 increasing the culture on a large scale are being provided. 



The way in which this liquid culture may be introduced into the 

 soil varies somewhat with the character of the seed to be used and 

 the area of the field to be treated. With large seeds it is often more 

 convenient to simply soak them in the fluid and then after they are 

 sufticiently dry to sow them in the ordinary way. In other cases it is 

 frequently more feasible to introduce the liquid culture directly into 

 the soil. This may be done by spraying, or perhaps a simpler method 

 is to mix the culture thoroughly with a wagonload of earth and then 

 to distribute and harrow this in just as a fertilizer would be handled. 

 Inoculations of this character have been tried on a laig'e scale in prac- 

 tical field experiments, and the results have been so satisfactory that 

 the Department of Agriculture will probably soon be able to begin 

 the introduction of cultures into such localities as are now deficient in 



* The Vegetable Pathologist has communicated with Mr. Moore, with a view to 

 securing a supply of the cultures. [Ed. journal.] 



