Lona (1946) was the first to demonstrate that in Xanthium receptors of graft combinations can function as donors in newly made graftings, suggesting an autocatalytic multiplication of the floral hormone. Wellensiek (1966) found the same for Silene. In order to investigate whether the floral hormones in Xanthium and Silene are identical, graftings between the two species were made. Remarkably enough, graftings of vegetative Silene receptors on generative Xanthium donors keep alive for some weeks and some graft union seems to have taken place. Finally the Xanthium stocks die and this ends the graft combination. The difficulty could be overcome by regrafting the Silene receptors on new vegetative Silene stocks, 3 to 7 weeks from the first grafting. This has resulted in some flowering Silene receptors under conditions where comparable control graftings never flowered. The photo illustrates the procedure.