Root tips of Hyoscyamus niger were cultivated on agar or in liquid medium, and patterns of elongation and branching were investigated. The elongation of roots compared to branching, particularly tertiary root branching, was more effective in liquid medium than on agar medium. The number (0.06 per cm) of tertiary roots which branched out from secondary roots was far less than that (4.2 per cm) of secondary roots from primary root particularly in liquid medium. When the secondary roots were cut from the primary root in liquid medium, branching of tertiary roots was markedly enhanced, from 8.4 to 17.5. Scopolamine content in the cut roots increased by 46.3% compared to that in normal roots.