Phytogeography of the Eastern Desert flora of Egypt

328 species in total were recorded at 500 sites between 30 degrees 06' and 24 degrees 00'N in the Eastern Desert of Egypt. The occurrence of species was classified into 5 constancy classes: dominant, very common, common, occasional and sporadic. A sharp decrease in the number of recorded species was noticed along the N-S direction from Cairo-Suez road in the north to Aswan-Baranis road in the south (from 179 to 23), and an increase along the E-W direction from the Red Sea coast in the east to the River Nile Valley in the west (from 46 to 80). It was found out that geographical affinities affect the patterns of species distribution: 82 annual (therophyte) species are dominant life forms within the northern part of the study area, followed by 33 species in the southern part. Phanerophytes (trees) showed a decrease in their number from north (13 species) to south (9 species), but a slight increase from east (9 species) to west (10 species). Distribution maps of local geographical subtypes of each of the 4 major chorotypes are shown and a suggested improved phytogeographical map is presented.