Three methods have been adopted. By the first, as previously indicated, the grower perseveres in sowing clover at short intervals in the rotation. He may also add farmyard manure occasionally, and thus, through the inherent power of multiplication in the bacteria, they increase sufficiently to enable the land to grow good crops. By the second method, inoculating is effected through soil which is possessed of the requisite bacteria; and by the third, it is effected through the aid of a prepared product named nitragin. When fields are to be inoculated by using soil it is obtained from areas which have grown clovers successfully quite recently, and which are, therefore, likely to be well filled with the desired bacteria. In some instances the seed is mixed with the soil and these are sown together. To thus mix the seed with the soil and then sow both together broadcast or with a seed drill is usually effective, and it is practicable when minimum quantities of soil well laden with germs are used. In other instances the soil containing germs is scattered broadcast before or soon after the seed is sown. Considerable quantities of earth must needs be applied by this method. It should be remembered that each class of legumes has its own proper bacteria. Because of this, inoculation can only, or at least chiefly, be effected through the use of soils on which that particular class of legumes have grown, or which are possessed of bacteria proper to that particular species. In other words, bacteria necessary to the growth of vetches will not answer for the growth of clovers, and _vice versa_. Nor will the bacteria requisite to grow medium red clover answer for growing alfalfa. In other words, the bacteria proper to the growth of one member of even a family of plants will not always answer for the growth of another member of the same. But in some instances it is thought that it will answer. The study of this phase of the question has not yet progressed far enough to reflect as much light upon it as could be desired. It is certainly known, however, that alfalfa will grow on soils that grow burr clover (_Medicago maculata_) and sweet clover (_Melilotus alba_), hence the inference that soil from fields of either will inoculate for alfalfa. Nitragin is the name given by certain German investigators to a commercial product put upon the market, which claims to be a pure culture of the root tubercle organism. These cultures were sold in the liquid form, and it was customary when using them to treat the seed with them before it was planted. Their use has been largely abandoned, because of the few successes which followed their use compared with the many failures. But it is now believed that these cultures can be prepared and used so as to be generally effective and without excessive cost to the grower.