A study of the taxonomy and chorology of the Bulgarian species of Euphorbia has led me to consider their phytogeography; this entailed a closer view on the main features of florogenesis and distribution of subg. Esula in Europe. There are two problems concerned, viz. the origin of the two sections Tulocarpa (Raf.) Prokh. and Murtekias Prokh. which contain the most primitive and ancient species of the subg. Esula and furthermore a consideration of their mutual relationships and the main trends of their evolution within the subgenus. The data on the distribution of the species examined in the present paper have been taken from the works of Boissier (1862, 1879), Halacsy (1904), Fiori (1925), Hegi (1925), Hayek (1927), Eig (1932), Prokhanov (1933, 1949), Ade & Rechinger (1938), Rechinger (1938,1943, 1952, 1960), Czeczott (1939), Losa Espagna (1946), Diapoulis (1948), Prodan (1953), Vindt (1953), and Köie & Rechinger (1954/55).