Abstract: Eight species of Paphiopedilum subgenus brachypetalum were karyologically analyzed by root tips squash method. The result showed that the number of the somatic chromosome of these plants is 2n = 26, diploid. The karyotypes were as follows: P. emersonii 2n = 2x = 26 = 18m + 8 sm, index of the karyotypic asymmetry (As.k) = 59.90%; P. concolor 2n = 2x = 26 = 2M + 18m + 4sm + 2st, As.k = 56.90%; P.bellatulum 2n = 2x = 26 = 22m + 2sm + 2st, As.k = 56.10%; P. hangianum 2n = 2x = 26 = 22m + 4 sm, As.k = 58.64%; P. malipoense 2n = 2x = 26 = 20m + 6sm, As.k = 59.41%; P. jackii 2n = 2x = 26 = 14m+ 10sm + 2st, As.k = 63.00%; P. armeniacum 2n = 2x = 26 = 24m + 2sm, As.k = 55.05%; P. micranthum 2n = 2x = 26 = 20m + 6sm, As.k = 56.91%. According to Stebbins classification of karyotypic asymmery, the karyotype of P. concolor, P. bellatulum and P. hangianum belonged to “2A”, the others belonged to “2B”. The diploid mainly consisted of metacentric and submetacentric chromosomes, but not satellites. Moreover, results of this karyological study provided some references on cytotaxonomy for system evolution of Paphiopedilum.

Key words: Orchidaceae, Paphiopedilum, Subgenus brachypetalum, Chromosome number, Karyotype