10 -C'lECrLAR XO. 113, BITJEAI; OF PLANT IXDL'STEY. 



nodules upon other ])lants of the same spei'ies m different locaHties. 

 Owmg to the fact that different legumes are constantly bemg mtro-- 

 dticed mto agricnlttiral regions, the importance of bemg able to dis- 

 semhiate the nodtde-forming bacteria is obviotis. For many types of 

 legumes this is desnable, not only from the standpoint of making the 

 crop a better nitrogen fixer and better soil renovator, btit because for 

 most legumes the crop is acttially larger when properly inoculated. 

 Pure-cidture moculation is less certain than moctdation by means of 

 soil from old, weU-moculated fields, though of course it is free from 

 the danger of introducuig troublesome weed seeds or plant diseases. 



WORK OF THE BUREAU OF PLANT INDUSTRY. 



The Bureau of Plant Industry is carrying on field experiments to 



determhie, if j^ossible, what soil conditions are most favorable for the 



successful moculation of legummous crops by the tise of pure cultures 



and also to determuie under what conditions it is useless to attempt 



to moculate certaui of the legtimes withotit some radical change in 



the method of fertilizing or cultivating these fields. To extendi this 



experimental work as far as possible, the Department of Agriculture 



is willmg to supply cultures in any reasonable quantity, ret^uiring 



only the fihing m of blank reports wliich are occasionally forwarded 



for this purpose. 



CONCLUSION. 



A casual review of the present status of soil bacteriology shows that 

 it is a stibject of ahnost bewildering complexity, but very intimately 

 associated with the normal physiology of all crop plants. By learning 

 what functions must be performed m the soil and by studymg each 

 gi^oup of organisms that has a measurable function, we beheve that 

 we can learn how to enhance the desnable activities of the living soil 

 and to check the undeskable ones. TTe may never find another rela- 

 tionship so shnple as that existmg between the legume crop and the 

 nodule bacilltis or one which we can control so sunply from a central 

 laboratory: but surely a thorough comprehension of what happens 

 m the soil will teach us how to maintam the fertility of the soil more 

 surely than blind and rather purposeless experimentation. The great 

 majority of plat tests of fertilizers illustrate the unpossibihty of satis- 

 factory deductions from experiments entnely upon an empirical 

 l)asis. AYe must deal in ieons and not in generations if agricultural 

 science is to be advanced by the cut-and-try method. 



[Cir. 113] 



