A Factor in Clover Nodule Formation Associated with the Volume of the Medium Occupied by the Roots

Abstract

IN the course of experiments involving the growing of clover seedlings (Late-flowering Montgomeryshire Red) on agar medium in test-tubes, it was noticed that the number of nodules produced per plant depended upon the number of individual plants occupying the same tube. As the nodule bacteria were present in very large numbers, this variation in nodulation cannot be due to paucity of organisms; indeed the question raised is rather why so few nodules are formed on plants in spite of the massive infections of the root hairs which are known to occur¹.