LEGUMINOUS PLANTS. 113 



ratory of Plant Physiology, the Department of 

 Agriculture at Washington has shown that "the 

 bacteria, when grown upon nitrogen-free media. 

 will retain their high activity if they are care- 

 fully 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-formine orcjanisms, and 

 then by allowing these cultures to become dry, 

 the bacteria can be sent to any part of the 

 United States or the world, and yet arrive in 

 perfect condition. Of course, it is necessar)- to 

 revive the dry germs by immersion in water, 

 and, with the addition of certain nutrient salts, 

 the original number of bacteria is orreatlv in- 

 creased if allowed to stand for a short time. 

 Frequently twenty-four hours are sufficient to 

 cause the water in a pail to turn milky white 

 with the number of orcranisms formed in that 

 time. Thus, by sending out a dry culture sim- 

 ilar 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 ob- 

 tained 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 the land is very small." The dry cul- 

 tures may be obtained from the United States 

 Department of Agriculture without cost. 



