The Potato Eelworm Hatching Factor 4. SOLANUM NIGRUM AS A SOURCE OF THE POTATO EELWORM HATCHING FACTOR BY P. B. RUSSELL, A. R. TODD AND W. S. WARING

It has been known for some time that the root excretion of several species of Solanum stimulates the hatching of larvae from the cysts of the potato eelworm, Heterodera ro8tochien8i8 (Franklin, 1940). The isolation ofthe active principle in root excretion and the investigation of its chemical nature was first attempted, using the leachings from potato plants (Hurst, 1935, 1937), but the method of production was cumbersome and a more convenient source of material was found in tomato plants. The tomato plants were more easily grown indoors than potatoes, and gave a very active excretion. As work on the chemical nature of the active principle developed (Calam, Raistrick & Todd, 1949; Marrian, Russell, Todd & Waring, 1949), greater demands were made upon production of starting material for the investigation, and necessitated the growing of many thousands of tomato plants during a season. It became clear that if the scale of the work continued to expand a new source of root excretion, which could be easily and cheaply grown out of doors on a large scale, would be welcomed to replace the growing of tomato plants under glass. With this end in view, a small scale outdoor experiment with Solanum nigrum was carried out during 1943 at the suggestion of Sir E. J. Salisbury, F.R.S., who also very kindly supplied the seeds, and the yield, quality and nature of the root excretion were examined.