198 • 



gin, and as we had not at hand at that time a field of any one 

 of the true clovers, it was decided to try the efl:'ect, as an inoc- 

 ulating material, of earth from a field of lespedeza or Japan 

 clover. This earth was sown at the rate of 720 pounds per 

 acre, broadcast, and harrowed in with the crimson clover seed. 

 Although the earth employed was well supplied with the 

 germs which cause the development of tubercles on lespedeza 

 plants, the crimson clover plants growing on the plots Mhere 

 it was applied formed no tubercles and failed utterly, attain- 

 ing a height of only about three inches. 



Numerous experiments conducted by the writer accord 

 with European experiments, which show that, with few ex- 

 ceptions, the inoculation of any leguminous plant can be 

 affected only by the root-nodule bacteria from a plant belong- 

 ing to the same genus. Thus the germs found in lespedeza 

 tubercles have no power to originate tubercles on crimson, 

 red or white clover ; vetch germs have likewise no inoculating 

 power toward the clovers, alfalfa, etc. 



The first word in the botanical name of a leguminous 

 plant generally gives the key by which to determine whether 

 its root-nodule bacteria are capable of inoculating any other 

 given leguminous plant. The general rule is this : If the 

 first word (generic name) of any two legumes is identical, the 

 root-tubercle bacteria on either are capable of causing tuber- 

 cles to grow on the other. Examples to illustrate this prin- 

 ciple follow : (a) Crimson clover ( Trifolium incarnatuni)^ red 

 cXovQV {Trifolium.pratense)^ white or creeping clover {Tri- 

 folium repens), inoculated with the same material ; (b) alfalfa 

 {Medicago saliva), bur clover {Medicago maculata), inocu- 

 lated wich the same material. 



The above rule does not cover all cases ; for example, the 

 root-nodule bacteria of the garden pea is capable of inoculat- 

 ing vetch, in spite of the fact that the first or generic names 

 of the two plants are not identical. 



Natural Methods of Inoculation. 



The fact that clovers and clover-like plants have inhabited 

 the earth for ages and have regularly formed tubercles with- 



