The present flora thoroughly covers the bryophytes of the Arabian Peninsula and Socotra island, with keys to all species, notes on the occurrence of the species in the different countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, United Arab Emirates, Yemen) and distribution maps. The flora includes one hornwort, 50 liverworts and 173 mosses. Altogether, 224 species are known from that area. A short overview on the bryofloristic exploration of the Peninsula, the phytochorial elements, and a phytogeographical analysis of the bryoflora are given. Typical of the monsoon-influenced xerotropical southwestern and southern border mountains of the Arabian Peninsula (summer rainfall area) as well as Socotra, are numerous Palaeotropical and Afro-montane taxa indicating the strong floristic relationships between southern Arabia and Africa In contrast, the arid and semi-arid parts of inner Arabia (winter rainfall area) are dominated by drought-adapted and drought-tolerant taxa of probably xerothermic-Pangaean and circum-Tethyan origin. They show a number of xeromorphic adaptations (xeropottioid and xerothalloid life syndrome) for life under desert conditions. The phytogeographical analysis of the bryoflora, as well as the distribution of thalloid and leafy liverworts, respectively acrocarpous and pleurocarpous mosses, demonstrate that there is a clear phytochorial border across the Peninsula, frequently correlated with climatic conditions (winter rainfall/summer rainfall line).
