An experience reported by Professor Herbert W. Mumford, of the Animal Husbandry Department of this university, will be of interest and value in this connection. Professor Mumford commonly grows clover in his rotations on his own private farm, but he states that at one time one particular field was cropped continuously with timothy, oats, and corn for some six years or more without any clover whatever. It was then again seeded to clover, but the crop made a complete failure, although on other land where clover had been grown more recently a successful clover crop was grown from the same kind of seed seeded at about the same time. The following year this particular field was again seeded to clover. This time the “catch” was not a total failure, but it was too poor to save, and it was plowed up and the land again seeded to clover the next year, and an excellent catch of clover resulted. After this, clover was frequently grown on this field, and no special difficulty was had in getting good crops. While the failure of clover may often be due to drouth, and in some places due to soil acidity (lack of lime), and sometimes even due to an insufficient supply of available phosphorus or of potassium, we now know with certainty that it sometimes fails because of the absence of the nitrogen-gathering bacteria, especially on land which has never grown clover, and probably also on land which has not grown it recently. We should always remember that the bacteria do not thrive in strongly acid soils. Even though they may sometimes live in such soils and perhaps produce some tubercles upon the roots of certain hardy, strong growing legumes, like cowpeas, nevertheless we are obtaining some strong evidence that in such acid soils they have but little power to gather nitrogen from the air. That ground limestone is the most economical and satisfactory material to use in correcting the acidity of soils is strongly indicated by the information we have thus far obtained. On the upland prairie soils of the Lower Illinoisan Glaciation where red clover has never been grown successfully, largely because of the acidity of the soil, it will undoubtedly be helpful and profitable not only to correct the acidity of the soil with ground limestone, but also to secure infected soil from some field of timber land or bottom land where red clover is growing, well provided with root tubercles, and inoculate the field with it. This soil should be collected to a depth of three or four inches and scattered over the prairie land at the rate of a few hundred pounds per acre at the time the clover is seeded or before. THE COWPEA BACTERIA. Plate 2 is made from a photograph of a cowpea root with the tubercles upon it. This illustration shows the cowpea tubercles at nearly natural size, which is about as large as the seed of ordinary garden peas. [Illustration: PLATE 2. COWPEA ROOT TUBERCLES, NATURAL SIZE.]