Abstract.Droopy mutant of potato (Solanum tubero‐sumL., groupPliureja) wilts because of excessive stomatal opening (Waggoner&Simmonds, 1966). Progeny of the cross between potato clones C.P.C. 4461 and C.P.C. 4463 showed characteristics similar to those of the original droopy potato. These plants wilted at high vapour pressure deficit and their stomatal conductances in the light and the dark were higher than those of normal plants. Conductances were reduced by applied abscisic acid (ABA), but stomata remained partially open even when guard cells were plasmolysed. Leaves of droopy plants accumulated very little ABA when water‐stres