BACTERIA AS FERTILIZERS. 



BY DR. GEORGE T. MOORE, WASHINGTON, D. C. 



AXNUAL LECTURE UNDER THE JOHN LEWIS RUSSELL BEQUEST. 



Abstract of an illustrated lecture delivered before the Society, 

 January 2.3, 1904. 



It is hardly necessary for me to discuss in detail the effect of 

 leguminous crops upon soils or the necessity for the roots of 

 these crops being provided with the proper nodules in order to 

 obtain the greatest good from them. You all know how neces- 

 sary nitrogen is in the soil, and any means calculated to increase 

 the quantity of this most important plant food is, of course, of 

 great practical value. From the earliest days of agriculture it 

 has been recognized that all plants belonging to the Leguminosae, 

 that is, peas, beans, clover, alfalfa, etc., had a decidedh^ beneficial 

 effect upon the soil, but it is only within recent years that we 

 have been able to explain this phenomenon. 



Although it has been a matter of common observation that the 

 roots of leguminous plants were usually provided with peculiar 

 swellings or nodules, these were popularl}^ supposed to be due to 

 the bites of worms or insects, and that they were directly con- 

 nected with the fertilizing power of the plant was not discovered 

 for many years. Even after it was shown that leguminous plants 

 devoid of these nodules were unable to benefit the soil, there was 

 the widest difference of opinion as to why they appeared upon 

 some i)lants and were absent from others. Now we know that 

 the legume nodule is the direct effect of the presence of myriads 

 of bacteria which have made their way into the roots through 

 the root hairs, and as a result of the irritation the plant manufac- 

 tures the nodule, each cell of which is full of bacteria. 



Although it is true that thousands of acres of land in this 

 country and abroad are well stocked wath these nodule-forming 

 bacteria, it is likewise a fact that there is equally as much land 



