both plants has already been suggested in the agricultural press. During the season of 1903 the writer spent some time in the northern part of Illinois in connection with the general and detail surveys of Illinois soil. Many new fields of alfalfa were observed, and they were carefully examined for root tubercles. In Winnebago County, where sweet clover is very prevalent along roadsides and in waste places, it was noted that the abundance of root tubercles on the alfalfa plants seemed to be closely related to the presence of sweet clover in the vicinity, strongly indicating that the bacteria which live upon sweet clover were also at home upon the alfalfa roots. These indications were strengthened by further investigations in Lake County, especially upon the Fowler farm, near Lake Villa, where a field of alfalfa seeded last spring without artificial inoculation was found to be thoroughly infected with the bacteria, and growing vigorously with a good dark green color. This field had a few sweet clover plants growing in it, and the borders of the field were covered with sweet clover. Other fields of alfalfa seeded in the neighborhood at the same time, but upon soils where sweet clover had not grown near by, were apparently complete failures, many of the plants having died and most of those still living being only a few inches high, very weak, and yellow or pale green in color.[7] In order to obtain more absolute knowledge regarding this important subject, a series of pot culture experiments has been carried on under controlled conditions in the pot culture laboratory at the university. Five pots were filled with sterilized sand which was practically devoid of plant food. A supply of phosphorus, potassium, and all other mineral elements necessary for the growth of plants was added to each of the five pots, care being taken to keep the sand practically free of combined nitrogen. Alfalfa seed were then planted in each of the five pots, and at the same time four of the five pots were inoculated as follows: Pot No. 1.—Not inoculated (check pot). Pot No. 2.—Inoculated with bacteria obtained from infected alfalfa soil. Pot No. 3.—Inoculated with bacteria obtained from alfalfa root tubercles. Pot No. 4.—Inoculated with bacteria obtained from infected sweet clover soil. Pot No. 5.—Inoculated with bacteria obtained from sweet clover root tubercles.