L’Alguier d’Agathe de Gourcuff is an herbarium of seaweeds, conserved in the Bibliothèque d’Etude of Brest. Realized in 1838, this object is presented as a book containing 60 species of seaweeds collected at Le Pérennou, on the banks of the Odet river, in the country of Quimper. Each species is presented by an etiquette with the seaweed name in French and not in Latin, which is unusual for a scientific work-like. However, the author, a women, Mademoiselle Agathe de Gourcuff, mentions its main source, the Botanicum Gallicum, which is a book in Latin version, that means she was able to read that language. Moreover, she communicates names of former and contemporary authors that she read in order to make her herbarium.