Druse crystals in the stem and leaf cross sections of Humulus lupulus . (A) Druse crystals in the pith cells of the stem. (B) Druses and crystal sands in the pith cells of the stem. (C) Druse crystal in leaf mesophyll cells. (D) Druse crystals around the vascular bundle (Dc: Druse crystals; Cs: Crystal sands).