Abstract: Nomocharis forrestii Balf. f. from Zhongdian, Yunnan, was cytologically investigated in this wrok. There were two cytotypes in N. forrestii populations. The reference karyotype of A cytotype was 2n=24=2m (2SAT) +2sm+8st (4SAT) +12t (2SAT). In this cytotype, there was no satellite in the long arms of the 3rd pair, which was homozygous. The reference karyotype of B cytotype was 2n=24 = 2m (2SAT) + 2sm+8st (2SAT) +12t (3SAT). In B cytotype, there was an obvious satellite in the long arm of one chromosome in the 3rd pair, but no satellite in the long arm of the other. This was heterozygous. The ratio between the cytotypes was approximately lA: 2B in the population. The karyotype in N. forrestii was similar to that in the genus Lilium, 2n=24, particularly the chromosomal morphology of m-chromosomes or sm-chromosomes. However, the secondary constrictions of the m-chromosomes was more obvious and greater in N. forrestii. Numerous aberrant karyotypes in N. forrestii were found in the somatic cells. The structural aberrations include breakage, inversion (incl. pericentric inversion), translocation (incl. Robertsonian translocation), deletion, somatic orossing over between the homologous chromosomes, etc. In the aberrant karyotype (1), an obvious deletion took place in one chromosome or unequal translocation took place in one chromosome of the 1st pair, and a fragment was added to the long arm of one chromosome as a result of translocation in the 7th pair. A dicentric chromosome was found between two chromosomes from 8th and the 12th pair, which resulted in 2n=23. In aberrant karyotype (2), translocation or deletion took place in the 5th, 6th, 7th and 10th pair. There were 4 B-chromosomes in the aberrant cell. In the aberrant karyotype (3), the long arm of one chromosome was found to have a deletion in the 6th pair. A dicentric chromosome was generated between two chromosomes from the 9th and the 10th pair, which results in 2n=23. There was one B-chromosome in the aberrant cell. In the aberrant karyotype (4), a pericentric inversion took place in the 1st pair, and an unequal translocation occured between the 1st and the 6th pair, which changed the first pair from m-chromosomes into st-chromosomes. The long arm of one chromosome carried a remarkable deletion in the 8th pair. In the aberrant karyotype (5), a Robertsonian translocation took place between two chromosomes from the 6th and 7th pair, and a fragment was added to the long arm of one chromosome as a result of the translocation in the l2th pair. In the aberrant karyotype (6), breakage occured near or at the centromere of one chromosome of the 1st and the 6th pair, which resulted in 2n= 26. Before the breakage, the unequal crossing over had taken place between the homologous chromosomes in the 1st and 6th pair, and an unequal translocation was found between two chromosomes from the 1st and 6th pair. Accoding to statistics of aberrant cells, the chromosomal aberration took place mainly in the 1st, 6th, 7th, 8th, 9th and 10th chromosomes, with rates of aberration 3337%. It is these chromosomes that often show polymorphism. From above, the karyotype of N. forrestii, is under strong differentation. So the somatic chromosome aberration with a high frequency is one of important factors in the intraspe-cific differentiation in N. forrestii.

Key words: Nomocharis forestii, karyotype, structural aberration, evolution