Abstract: The present paper deals with a karyotype of two species of the genus Ammopiptanthus. The chromosome numbers in root-tip cells of these two species are both 2n=18. The karyotype formulas of the two species are as follows: A. mongolicus K(2n)=18=10m+4m(SAT)+2sm+2st; A. nanus K(2n)=18=8m+2m(SAT) +2sm+2sm(SAT) +4sm(SC). Results obtained through chromosome examination have shown that they both belong to "2A" type of Stebbins’karyotypic asymmetry. But there are differences in chromosome formulas, it is assumed that A. nanus karyotype is a little more advanced than of A. mongolicus.

Key words: Ammopiptanthus, A. rnongohcus: A. nanus, Chromosome numbers, Karyotype