大黃 Dahuang

Cross Section

Phellem and Phelloderm of root mostly have removed. Phloem duct groups are obvious; parenchyma tissues are developed. Cambium is circular. Xylum ray is relatively dense, 2~4 rows of cells, with brown inclusion; ducts are not woodened, arranged loosely. Parenchyma cells have Calcium oxalate cluster crystals, with numerous starch grains.
Pith of root often has mucus cavity, scattered abnormal vascular bundles (star point), inner calyx-like cambium, xylum is inside of the phloem, and rays are in star shape.