Effective and Ineffective Association between Root–Nodule Bacteria and the Host Plant

MR. VINCENT, who courteously sent me a copy of this letter before publication, suggests that the juice from roots bearing effective nodules is more stimulating to the growth of Rhizobium as a result of effective association. This is in agreement with our views. We state in our paper1 (p. 489) that there is evidence of “an increased stimulating effect from juices of roots bearing effective nodules, possibly connected with the products of nitrogen fixation”.