Characteristics and Movement of the Flowering Stimulus from the Induced Leaf of Xanthium

1. A technique was used of photoinducing single-leaved Xanthium plants for the production of floral primordia, followed by removal of the leaf after various time intervals and under different dark and light conditions. This provided a method for studying (a) the time required for formation and translocation of the flowering stimulus from its site of synthesis, the leaf, and (b) the effect of light on its movement and lability. 2. The substance moves out of the leaf shortly after it is formed, and under certain conditions a total period of about 24 hours is adequate for formation and translocation of sufficient amounts of the floral stimulus to induce the formation of floral primordia at the apical meristem. 3. This flower-inducing substance is not destroyed by light while still in the leaf, and, in fact, the final effective amount normally does not move out of the leaf until the following light period. 4. Xanthium can be induced to produce flower primordia by subjection to a long continuous dark period no...