The results clearly show the very great value of the nitrogen-gathering bacteria in growing cowpeas. In each of the separate trials A, B, and C, the infected plants contained about twice as much total dry matter as the plants not infected. The infected plants also contained a much higher percent of nitrogen than the plants not infected, the infected plants containing 4.09 to 4.33 percent in the tops and 1.45 to 1.53 percent in the roots, while those not infected contained only 2.32 to 2.69 percent in the tops and .88 percent in the roots. Besides this, the tubercles on the infected plants contain 5.76 to 6.05 percent of nitrogen. In these young and rapidly growing plants the tubercles are much richer in nitrogen than any other part of the plant. It should be stated that as the plants approach maturity the nitrogen is largely absorbed from the tubercles and stored in the tops and roots. At the time these plants were taken up the tubercles actually contained more nitrogen than the roots. The infected plants contained nearly four times as much nitrogen as the plants not infected, and about three-fourths of the total nitrogen in the infected plants was obtained from the air. The roots and tubercles of the infected plants contained six to seven times as much nitrogen as the roots of the plants not infected. TABLE I.—FIXATION OF NITROGEN BY COWPEAS. =============================+========+========+========+========= COWPEA PLANTS. | Dry |Nitrogen|Nitrogen|Nitrogen -----------------+-----------+ matter,|content,|amount, |fixed by No. | Part | cgs. |percent.| cgs. |bacteria, | | | | | cgs. -----------------+-----------+--------+--------+--------+--------- A1—Ten plants, | Tops | 3580 | 4.09 | 146 | with bacteria | Roots | 620 | 1.45 | 9 | present. | Tubercles | 190 | 5.97 | 11 | | | ---- | | --- | | Total | 4390 | | 166 | 125 | +--------+--------+--------+ A2—Ten plants, | Tops | 1560 | 2.42 | 38 | without bacteria | Roots | 300 | .88 | 3 | | | ---- | | --- | | Total | 1860 | | 41 | -----------------+-----------+--------+--------+--------+--------- B1—Ten plants, | Tops | 3970 | 4.31 | 171 | with bacteria | Roots | 690 | 1.47 | 10 | present. | Tubercles | 300 | 6.05 | 18 | | | ---- | | --- | | Total | 4960 | | 199 | 140 | +--------+--------+--------+ B2—Ten plants, | Tops | 2060 | 2.69 | 55 | without bacteria | Roots | 430 | .88 | 4 |