It was concluded that internal sprouts do not arise from adventitious buds, but from ordinary buds which show at least some development of external sprouts. Internal sprouts exhibited negative geotropism, and whether the parent tuber or an adjacent tuber was penetrated depended mainly on whether the developing sprout happened to be on the upper or lower part of the tuber. Internal sprouts became more prevalent when external sprouts were rosetted, but could be found to some extent when external sprouts showed little branching. CIPC at dosages sufficient to inhibit most, but not all, external sprouting greatly increased internal sprouting, presumably through the production of rosette sprouts. Higher concentrations of CIPC inhibited all bud growth and hence eliminated both external and internal sprouting. MH reduced, and TCNB had no effect on, internal sprouting.