The Botanic Garden Museum of the Jagiellonian University (Cracow, Poland) possesses letters to Józef Rostafiński (1850-1928), a founder of Polish history of botany. The letters contain answers to his inquiry connected with his dealings with history of cultivated plants in Poland. Theinquiry questionnaire was published for the first time on 14th July 1883 in "Czas" (in Cracow) and it referred to 92 species. Within the next 4 months the questionnaire was printed by at least 30 Polish periodicals in a few versions (the most comprehensive one regarded to 129 species). 370 persons took part in the inquiry and sent up near 860 letters. Unfortunately, only 235 letters written by 136 authors have been preserved. Among participants there were such naturalists as: Władysław Boberski (1846-1891), Tytus Chałubiński (1820-1889), Józef Roman Chociszewski (1837-1914), Władysław Dybowski (1839-1910), Roman Gutwiński (1860-1932), Adam Kubaszewski (1847-1927), Zygmunt Morawski (1849-1907) and Maria Twardowska (1858-1907). Then correspondence is elaborated in this article in details. J. Rostafiński obtained by means of the inquiry vastly abundant information: about folk names of plants (ca. 15,5 thousand records), the ways and history of cultivation of those plants, about frequency of occurrence of given species, and about habits and folk beliefs connected with them. He never fully elaborated the obtained data.