Karyotypes of eight populations representing four species of the genus Allium were ana-
lyzed. Included in this study are first reports of the karyotypes for three species from China. All
species examined were diploids, except Allium caeruleum in which diploid, triploid and tetraploid
were found. The results of this study and chromosome data previously published show that: 1 ) the
basic chromosome number of sect. Haplostemon is x = 8, and the karyotypes of all the species in
this section belong to Stebbins' lA and 2A types; 2) polymorphism in satellited chromosomes
among different populations of the same and different species may play an important role in the ada-
ptability of the plants to the habitats; 3) some species of this section, such as Allium caeruleum and
A. macrostemon, appear to be karyotypically diverse at the infraspecific level, and some species
show intraspecific morphological variation and 4) the sterile triploid A. caeruleum and the sterile
pentaploid A. macrostemon increase population size vegetatively through multiplication of bulbs and
bulbils. The relationship of their habitats, breeding systems and polyploid in the section are dis-
cussed. Vegetative reproduction and polyploidy are important in the evolution of polyploid species of
sect. Haplostemon.
