Abstract: Based on the distribution data of 84 species of the genus Racomitrium in 20 geographical unites (suggested by “Index Muscorum”)in the world, Detrended Correspondence Analysis (DCA) and 3-Dimensional scatter plots were applied to study the distribution pattern of the genus. The results showed that 20 geographical units in relation to the distribution of Racomitrium in the world could be divided into north hemisphere region and south hemisphere region. The north hemisphere region (mainly from Laurasia) includes Am.1, Eur., As.1, As.2, As.3, As.5, Afr.1 and Oc., while the south region (mainly from Gondwana) includes Am.2, Am.3, Am.4, Am.5, Am.6, Afr.2, Afr.3, Afr.4, Austr.1, Austr.2, As.4, Ant.. The floristic characteristics of the two regions were also analyzed. The results show that the flora of the genus Racomitrium between North and South Hemispheres are obviously different. The groups of Niphotrichum and Codriophorus with lamina papillae mainly distributed in the North Hemisphere, and the taxa of the genus without lamina papillae widely distributed on both the hemispheres. Based on the distribution patterns of the genus Ptychomitrium in the world, the origination of the genus was also speculated, and it is possible that the genus Racomitrium originated before the division of the Pangaea, and the ancestors of Racomitrium are those without laminal papilliae.

Key words: Racomitrium, geographical distribution pattern, detrended correspondence analysis