THE PROBLEM OF THE EVALUATION OF ROTENONE-CONTAINING PLANTS

A study has been made of the rotations of the resins from three types of derris root, and of a fraction rich in toxicarol separated from two of them. No strictly quantitative relationship between their rotations and their toxicities to Aphis rumicis has been found. The addition of caustic potash in methyl alcohol to the benzene solutions of the resins induces a characteristic change from laevo- to dextro-rotation in the samples rich in toxicarol. The induced dextro-rotation then declines in value with time. This effect is shown by the "toxicarol" resin. The rate of the decline is accelerated by increasing the amount of methyl alcohol.
We are greatly indebted to the Copper Technical Bureau for gifts of the "Sumatra-type" root and of resins derived from this strain.
We wish to express our thanks to Mr C. Read for help during the course of this work.