Abstract: Allium Sect. Anguinum G. Don (Liliaceae) includes five species and three varieties. The results of investigation on 23 local populations, representing five species and one variety of this section, are as follows: (1) In this section, the basic chromosome number is x＝8, and the karyotypes of all the species belong to 2A type. All the populations have similar metaphase chromosomes. The similar karyotypical features support the viewpoint that Sect. Anguinum is a natural taxon. (2) Despite the fact that the karyotypicat features appear to be similar, karyotypical differences exist in some populations within the same species or among the species. First, there are various levels of ploidy. Second, the occurrence, number and shape of B chromosomes are variable among the populations. Third, as for the satellite chromosomes, there is a polymorphism in occurrence of the tandem satellites. (3) Highly sterile triploid of Allium ovalifolium has a kind of stolon and expands population by vegeta tive propagation. (4) According to widely geographical distribution and relatively old geological history of the geographical area, A. victorialis is considered as a primitive species in this section. This species, by means of geographical (gradual) speciation, has evolved step by step to the other species. (5) According to the geographical distribution and evolutionary process of Sect. Anguinum, it is proposed that the region from the Hengduan Mountains to the Qingling Range of China be the center of present distribution and differentiation of thesection.

Key words: Allium, Sect. Anguinum, Karyotype, Polyploid, B chromosome, Intraspecif-