212 SYSTEMS OF PERMANENT AGRICULTURE 



immediately sift over them sufficient dry, pulverized, infected soil 

 to absorb all of the moisture, thus furnishing a coating of infected 

 soil for every seed. The seed should be shoveled over a few times, 

 then screened, and planted within a day, or spread out to dry, 

 after which they may be kept as long as though not covered with 

 dust. The coat of thoroughly infected soil provides a much better 

 inoculation than is common from the use of artificial cultures, 

 and it does not interfere with drilling the seed immediately after 

 treatment. If this method is used for inoculating small seeds, such 

 as alfalfa, greater care must be taken to screen them afterward to 

 prevent clusters of seeds from remaining glued together. 



If seeds are moistened, they should either be planted very soon 

 thereafter or spread out and thoroughly dried, otherwise they are 

 likely to mold and lose vitality. Infected soil should never be long 

 exposed to bright sunshine, which is very destructive to all forms 

 of bacteria. 



There has been much discussion during recent years concerning 

 the development of unusually virile bacteria, but even if it were 

 possible to develop and maintain in the soil bacteria of greater 

 nitrogen-fixing power, it is a question whether the discovery would 

 have great practical value (especially after the first year) , for the 

 simple reason that bacteria multiply with such tremendous rapid- 

 ity that we may soon have many times the number of bacteria that 

 are really needed to do the work. In other words, the increase in 

 numbers may result in just as great efficiency as would result from 

 any increased power of the individual bacteria. One who carefully 

 studies the formation of root tubercles on plants growing on soils 

 in varying conditions or degrees of infection will observe that on 

 plants sparsely infected the individual tubercles or clusters develop 

 to enormous size, comparatively speaking; while in well-infected 

 soils the individual tubercles are much smaller, and clusters scarcely 

 form. It is also observed that the marked effect on the growth, 

 color, and composition of the plant is produced even though only 

 a half-dozen large tubercles form on the roots. It is very evident 

 that the relationship between the bacteria and the host plant is 

 such that if the soil is sparsely infected, so that the roots come in 

 contact with but few bacteria, and but few tubercles are started, 

 those few tubercles will be so enlarged, either in individuals or as 



