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

But it is now

compared with the many failures. believed that these cultures can be prepared and used so as to be generally effective and without excessive cost to the grower.

In preparing cultures it has been found that by gradually reducing the amount of nitrogen in the culture of media, it is possible to increase the nitrogen fixing power in these germs from five to ten times as much as usually occurs in nature. It is now known that the bacteria thus grown upon nitrogen free media retain high activity if carefully dried and then revived in liquid media at the end of the varying lengths of time. Some absorbent is used to soak up the tubercle-forming organisms. The cultures are then allowed to dry, and when in that condition they can be safely sent to any part of the country without losing their efficacy. It is necessary to revive the dry germs by immersing them in water. By adding certain nutrient salts the bacteria are greatly increased if allowed to stand for a limited time as short, in some instances, as 24 hours. The culture thus sent out in a dry form, and no larger than a yeast cake, may thus be made to furnish bacteria sufficient to inoculate not less than an acre of land. It is stated that the amount of inoculating material thus obtained is only limited by the quantity of the nutrient water solution used in increasing the germs, so that the cost of inoculating land by this process is not large. The culture may be applied by simply soaking the seed in it, by spraying the soil, or by first mixing the culture into earth, spreading it over the field and then harrowing it. Inocu

lations thus tried under the supervision of the United States Department of Agriculture have proved quite successful.

Where any legume is extensively grown surrounding soils come to be inoculated through the agency of winds and water. The increase brought to the yield of plants on various soils runs all the way from a slight gain to 1000-fold. And when soil is once inoculated it remains so for a long time, even though the proper legume should not be grown again on the same soil.

The amount of nitrogen that may thus be brought to many soils by growing clover and other legumes upon them is only hedged in practically by the nature of the rotation fixed upon. An acre of clover when matured will sometimes add 200 to 300 pounds of nitrogen to the soil under favorable conditions. Where the soil contains the requisite bacteria, the young plants begin to form tubercles when but a few weeks old, and continue to do so while the plant is active until mature. That the plants use much of the nitrogen while growing would seem to be clear, from the fact that toward the close of the growing season the tubercles become more or less broken down and shrunken.

CHAPTER III

MEDIUM RED CLOVER

Medium Red Clover (Trifolium pratense) is also known by the names Common Red Clover, BroadLeaved Clover and Meadow Trefoil. The term medium has doubtless come to be applied to it because the plants are in size intermediate between the Mammoth variety (Trifolium magnum) and the smaller varieties, as the Alsike (Trifolium hybridum) and the small white (Trifolium repens). But by no designation is it so frequently referred to as that of Red Clover.

This plant is spreading and upright in its habit of growth. Several branches rise up from the crown of each plant, and these in turn frequently become branched more or less in their upward growth. The heads which produce the flowers are nearly globular in shape, inclining to ovate, and average about one inch in diameter. Each plant contains several heads, and frequently a large number when the growth is not too crowded. When in full flower these are of a beautiful purple crimson, hence, a field of luxuriant red clover is beautiful to look upon. The stems of the plants are slightly hairy, and ordinarily they stand at least fairly erect and reach the height of about one foot or more; but when the growth is rank, they will grow much

higher, even as high as 4 feet in some instances, but when they grow much higher than the average given, the crop usually lodges. The leaves are numerous, and many of them have very frequently, if not, indeed, always, a whitish mark in the center, resembling a horseshoe. The tap roots go down deeply into the soil. Usually they penetrate the same to about 2 feet, but in some instances, as when subsoils are open and well stored with accessible food, they go down to the depth of 5 or 6 feet. The tap roots are numerously branched, and the branches extend in all directions. When they are short, as they must needs be in very stiff subsoils and on thin land underlaid with hard soil, the branches become about as large as the tap roots. It has been computed that the weight of the roots in the soil is about equal to the weight of the stem and leaves.

Medium red clover is ordinarily biennial in its habit of growth, but under some conditions it is perennial. Usually in much of the Mississippi basin it is biennial, especially on prairie soils. On the clay loam soils of Ontario, Ohio, Michigan, Wisconsin, Indiana and some other States, it is essentially biennial, but many of the plants will survive for a longer period. In the mountain valleys in the Northwestern States, and on the Pacific slope west of the Cascade Mountains, it is perennial. Medium red clover meadows in these have been cut for several successive years without re-seeding the crop. The duration of this plant is also more or less influenced by pasturing as compared with cutting for seed. Grazing the plants has the effect of prolong