The article deals with the early stages of research by Jozef Tomasz Rostafinski (1850-1928), one of the greatest Polish biologists, a well-known botanist and humanist. Presented in the article is the correspondence between Rostafinski. and his friend and teacher, the French scientist Jean Baptiste Edouard Bornet (1828-1911). This correspondence is of great value for the assessment of Rostafihski's early research on algae. The correspondence is stored at a library at the Laboratory of Cryptogamy (PC) of the National Museum ofNaural History (MNHN), consituting a small but homogenous and very interesting collection. It consists of eleven well-preserved manuscripts in the French language, which are kept among the materials connected with Edouard Bornet. The letters in the correspondence concern a number of topics, including scientific ilysis, descriptions of J. Rostatinski research on algae, numerous questions connected h Laminariaceae, as well as other issues, relating to Rostafitiski's friend, E. Janczewski, the Villa Thuret in France, and to the problems with his'mail that Rostatinski expended in March 1876. It is well known that a major study by Rostafinski was lost and disappeared before publication - the study in question was a large monograph of the Laminariaceae family of algae, which earned Rostafinski a gold medal in a competition organized by the Royal Academy of Sciences in Brussels in 1877. A new trace of the monograph can be iind in his letters to Bornet, in which there is reflected a fragment of an authentic report the algae research. The letters also contain references of the work of other scientists, e.g., G. Thuret 817-1875), E. Janczewski (1846-1918), A. de Bary (1831-1888), A. de Jolis 823-1904) and M. Woronin (1838-1903). The current article forms part of a research project sponsored by the French government. The author of the article would like to express her gratitude to Dr. P. Daszkiewicz, r. D. Lamy, Prof. J.-M. Drouin, Prof. B. de Reviers and Mr. F. Bouzzat.