One day from the history of the Great Physical Auditorium: Nikolai I. Vavilov’s report on 4 June, 1920

The Great Physical Auditorium of Saratov University is one of the best university lecture halls in Russia, it has a wonderful interior, large capacity and good acoustics. It also has a wonderful history. One outstanding event that took place in the Great Physical Auditorium 100 years ago is described in the article. On June 4, 1920, Nikolai I. Vavilov, professor of the agronomic faculty of Saratov University, made a presentation on «The law of homologous series in variation" to the participants of the III All-Russian Breeding Congress. The law determines the fundamental features of the evolution of plants and living organisms from a genetic standpoint. It influenced the subsequent development of biology, genetics, plant growing, breeding, biophysics and agrophysics on a global scale. The article describes the versatile activities of Nikolai I. Vavilov in 1918-1921 on the post of professor at Saratov University as a teacher, organizer of student practices and expeditions, as a deep scientist and analyst. His report was met with great enthusiasm by the participants of the Breeding congress. The law of homologous series in variation may be compared with the periodic law by Dmitry I. Mendeleev. The article was written by using the materials of the Breeding Congress, the Vavilov's collection of the Saratov Regional Museum of Local Lore, the memoirs by the participants of the Congress, scientific publications reflecting the modern significance of the law by Nikolai I. Vavilov. More than 50 congress participants, captured in the historical photograph of June 4, 1920, are named. The article notes interesting parallels between the III All-Union Congress of Breeding in 1920 and the VI Congress of the Russian Association of Physicists in 1928, which was also held within the walls of the Great Physical Auditorium. Sergei I. Vavilov was secretary of the Physical congress. The outstanding role of the brothers Nikolai I. and Sergei I. Vavilovs by organization of scientific activity in Russia is emphasized. The topic of modern scientific conferences held at the Great Physical Auditorium is named. It is concluded that the Great Physical Auditorium of Saratov University has acquired the significance of one of the important communication scientific centers of Russia and the world.