medulla tetrapanacis, also known as Akebia, Akebia and Hemp Seed. A shrub or small tree of Araliaceae. Originated in South China and Taiwan Province, it is the raw material for making rice paper. Taking out the central tissue of the stem, surgical dressing and watercolor paper can be made. It rose in Guangzhou in the 19th century and was mainly used for export. Its themes mainly reflected the social life scenes and various figures in the late Qing Dynasty, such as officials, soldiers and brave figures, juggling pictures, textile pictures, playing pictures and so on. The works are vivid in shape, rich in color and vivid in characterization. It was deeply loved by westerners at that time because it adopted the western painting principles and reflected the local customs of China. However, because papyrus is easy to break, there are few large-size works, and it is difficult to preserve, so there are not many handed down in China at present. In recent years, people have paid more and more attention to the grass-through painting, which is of great significance to the study of the early development of western painting in China.