The liberated alkaloidal fractions obtained from the seeds of nine species of Erythrina have been examined. Erysodine and erysopine were isolated in many cases. One new liberated alkaloid named erysonine was isolated from the seeds of one species. Erysonine has the empirical formula C17H19NO3. Certain preliminary facts about its constitution have been described. Erysonine possesses a curare-like action in frogs when administered by intralymphatic injection. The threshold dose is 100 mg./kg. © 1941, American Chemical Society. All rights reserved.