In ancient times, there were two types of "Juhong" came from the tangerines(Citrus reticulata) and the pomelos(C. grandis and its cultivars), which corresponded to Juhong and Huajuhong recorded in the Chinese Pharmacopoeia respectively. In different periods, Juhong basically came from the same species and the same medicinal parts, but there were also some differences. This article sorted out the ancient and modern literature, under the guidance of "Succession theory of Medicinal materials varieties" and "Change theory of Medicinal materials varieties"(XIE Zong-wan), and combined with field investigation, the evolution and reasons of the original plants and medicinal parts of Juhong were analyzed. In the Han Dynasty and before, the peel of tangerines and pomelos were both used as medicine. In the Southern and Northern Dynasties, the way tangerine peel was used was dried and aged, and then "soaked in hot water and scraped off the mesocarp", which had the essence of only using exocarp as medicine of Juhong already, and its original plant was C. reticalata. In the Song Dynasty, the name of "Juhong" and its medicinal usage were recorded in book on materia medica, and the species and medicinal parts of tangerine were inherited from the previous dynasties. The way tangerine peel was used was only dried and aged without removing the mesocarp. The medicinal material obtained by the way was called Chenpi(dried and aged tangerine peel). The item "Juhong" listing as a separate medicinal material was first recorded in the Collected Discussions from Materia Medica(Bencao Huiyan) in the Ming Dynasty. In the Ming Dynasty, the Dao-di habitat of Juhong was recorded as Guangdong province in most books on materia medica, and the original plants probably were C. reticalata and C. grandis 'Tomentosa'(Huazhou pomelo, a special cultivated species of C. grandis produced in Huazhou, Guangdong, which was recorded in the Chinese Pharmacopoeia as "Huajuhong"), according to the records in the local chronicles. During the Qing Dynasty and the Republic of China, the original plants of Juhong were C. reticalata and C. grandis 'Tomentosa'. Of the two, the latter one was considered as the better. As far the medicinal part, it was still the exocarp, while the whole young fruit of C. grandis 'Tomentosa' began to be used as medicine. After the founding of The People's Republic of China, the exocarps of Citrus reticalata, C. grandis and C. grandis 'Tomentosa' were listed in the Chinese Pharmacopoeia under "Juhong". From the Northern and Southern Dynasties to the Republic of China, C. grandis exocarp was a fake of Juhong. Therefore, it was contradictory to historical records that C. grandis exocarp was listed in the Chinese Pharmacopoeia as Huajuhong. Juhong had been divided into two types as "Juhong" and "Huajuhong" since 1985. The medicinal part of Huajuhong was only the exocarp of immature and nearly mature fruits, but not the whole young fruit, the actual mainstream medicinal part of Huajuhong. The results are helpful to clarify the historical evolution of species and medicinal parts of Juhong and Huajuhong. It is suggested that in the next edition of Chinese Pharmacopoeia, only C. grandis 'Tomentosa' should be included as the original plant of Huajuhong, and C. grandis should be deleted, and the young fruit should be added in the medicinal parts besides the exocarp of immature and nearly mature fruit.
Keywords: Citrus grandis ′Tomentosa′; Huajuhong; Juhong; change theory of medicinal materials varieties; herbalogical study; medicinal part; succession theory of medicinal materials varieties.