SUMMARYStomata on growing potato tubers are changed to lenticels by about the third internode from the apical bud (A‐3). In wet soil lenticels proliferate, while in dry soil the filling cells become suberized by about the fifth internode (A‐5).Lenticels did not proliferate in the field after mid‐August, and laboratory experiments on freshly harvested and stored tubers showed that lenticels proliferated less readily as tubers aged. Proliferation occurred more readily on stored tubers induced to sprout than on tubers from which the eyes had been removed, but nevertheless proliferation is unlikely during winter st