关键词: 农地制度, 农地制度, 制度变迁, 制度绩效

Abstract: There are about forty species of Brassica in the world, of which fifteen are distributed in China. The origin, evolution and spread of Brassica plants are discussed, and the point of view of author regarding some important problems about the systematics of Brassica in China has been put forward. The result shows: （1）The evolution of Brassica : An evolutionary line of form of Brassica in China is proposed based on compartment between Brassica and Capparaceae, and they are Sect.Pekinensis sect. Juncea and Sect.Oleracea. The earliest plant of Sect.Pekinensisis is B.parachinensis, but the earliest plant of Sect.Juncea is B.integrifolia(west)O E.Schulz. During the evolution of Brassica in China, the changes of leaves, petals, seeds polleu morphology, type of aperture, sculpture of exine are obvious, which are important in the evolution of Brassica. （2）The distribution of species: The Brassica are widely distributed throughout the Huanghe River Corridor and Changjiang River Corridor and Western Mountain Region of China. But the almost species of Brassica in China are distributed in Qinghai-xizang Plateau and its’ around Region. The result of study show that Western Region of China is variety centre of Brassica in China, it might be concluded that China is one of the original centres for Brassica, and Chinese Brassica did not come from the Mediterranean. （3）The origin and spread : The analysis of distribution pattern of species shows that the region is probably the place of origin of the genus. About four migration routes lead to the present distribution pattern.（a）From Tibet, Southern River Valley and Hengduan Mountain Northeast across the Qilian Mountain to west of the Huanghe Corridor and Tianshan Mountain;（b）From Tibet, Southern River Valley and Hengduan Mountain Northeast across Gansu, Ningxia, Shanxi, Hebei, to Northeast part of China;（c）From Tibet ,Southern River Valley and Hengduan Mountain southeast across Sichuan, Yunnan, Chongqing, along the Changjiang River to Guangdong, Taiwan provinces;（d）From Tibet, Southern River Valley and Hengduan Mountain Western to the Himalayas Region.