[60] It is asserted by some observers that the root-bacilli producing differently-shaped excrescences upon different legumes are distinct species; but this view is not sustained by the experiments of Nobbe and Hiltner, and seems intrinsically improbable. _Mode of Infection._—The infection is especially effectual when applied to the seeds before sowing; and for that purpose there may be used either the turbid water made by stirring up in it some earth of a properly infected field, or else water charged with a pure culture of the appropriate kind, commercially known under the name of nitragin, now manufactured for the purpose. Or else, the field to be sown may be infected by spreading on it broadcast, _and promptly harrowing in_, a wagon-load of earth per acre from a properly infected field. Such earth must not be allowed to dry, or to be long exposed to light. Specially effective (“virulent”) and hardy forms of such bacteria have been produced under artificial culture by Dr. Geo. T. Moore of the U.S. Department of Agriculture. These cultures can be sent by mail on cotton imbued with them, for the infection of seeds. It is very important that the bacillus should be present in the _earliest_ stages of the growth of the seedlings; otherwise the latter will undergo a longer or shorter period of starvation, unless the soil contains, or is furnished with, a sufficiency of available nitrogen to supply their immediate wants. When such a supply is very abundant, the legume crop will sometimes develop no nodules at all; but the best crops appear to be the result of a thorough infection, and abundant formation of the excrescences. _Cultural Results._—The marked results obtained in certain soils by inoculation with the legume-root bacillus are exemplified in the following table, showing results of experiments by J. F. Duggar, at the Alabama Experiment station.[61] TABLE SHOWING INCREASE OF PRODUCTION BY SOIL INOCULATION. ==============================+=======+========+================ PER ACRE. | TOPS. | ROOTS. | NITROGEN. | lbs. | lbs. | lbs. | Value. ------------------------------+-------+--------+-------+-------- Hairy vetch, not inoculated | 194 | 387 | 7 | $ 1.05 “ “ inoculated | 3045 | 1452 | 106 | 15.90 Crimson clover not inoculated | 106 | 266 | 4.3 | .65 “ “ inoculated | 4840 | 1452 | 143.7 | 21.25 ------------------------------+-------+--------+-------+-------- [61] Bull. Ala. Exp’t Station, No. 96, 1898.