Rule, Eduard von, botanist and known. Publicist from Gotha, longtime director of the Kaiserl. Botanical Garden in St. Petersburg (1815-1892). 5 letters and 1 postcard in the U.S. "E. Regel" or "E-V. Rule", of which 5 are all hands. 8 pp. gr. 4to, gr. 8vo and the postcard. St. Petersburg 1873-1888. To the paster. Botanist Anton Kerner von Marilaun (1831-1898), professor in Vienna and director of the botanical garden there. Exclusively on topics of botany: plant exchange, mutual collections and exhibitions as well as special questions on individual plants. 1 letter with printed letterhead "Directeur du Jardin Impérial de Botanique St. Petersbourg". - The postcard with some text loss by cutting out the stamp.