Algae are very diverse organisms and do not form a monophyletic group. In other words, blue and brown algae and most planktonic algae are unrelated to green and red algae. They vary greatly in size, ranging from less than a thousandth of a millimetre to over 50 metres.

The algae collection contains around 500,000 specimens including a great many types, estimated at 10,000. The specimens are dry preserved, mainly on herbarium boards, in a liquid or on microscope slides.

The collection was formally established with the creation of the Cryptogamy chair in 1904. Based on the botany chair’s collection, a large proportion of the specimens were reviewed and authenticated by É. Bornet; the collection was later considerably enriched by a bequest from him in 1911.

It includes specimens harvested from the early 18th century to the present day. The oldest specimens are those harvested by Sébastien Vaillant circa 1700 in the Paris region. The collection is also the result of the circumnavigation trips and great scientific expeditions organised by the Muséum or by the Ministry of Public Instruction. Specimens gathered by J.-B. Bory de Saint-Vincent, L. Desaules de Freycinet, J. Dumont d'Urville, L.-I. Duperrey, J. Gaimard, C. Gaudichaud-Beaupré, J. Hombron, C. Jacquinot, R. Lesson, J. Quoy and others are thus preserved there. Yet they also contain harvests by the great cryptogamists who took a particular interest in algae, like C. Montagne, and specialists from the 19th and 20th centuries such as: É. Bornet, A. de Brébisson, A. Gomont, R. Lami, P. Lefébure, J. Feldmann, G. Hamel, P. Hariot, M. Lemoine, L. Mangin, É. Manguin, H. and M. Peragallo, P. Petit, C. Sauvageau J. Tempère, and G. Thuret. As well as these specimens, there are those preserved in so-called “historical” herbaria, such as those gathered by J. Piton de Tournefort, A. von Haller, J.B. Lamarck, M. Adanson and the Jussieus.

Very consistent from the 19th century thanks to the many explorations that took place at that time. A 20th-century highlight of the algae collection is the number of harvests from the former French colonies. The collection has grown with recent harvests like those by F. Ardré, exchanges with major institutes like the Canadian Muséum of Nature, deposits of types and donations, recently including the J. Feldmann, F. Magne and R. Delépine collections. It is now expanding further as the Muséum resumes its great naturalist expeditions, particularly as part of Our Planet Reviewed, with the participation of the phycological group of the ISYEB (Institut de Systématique, Evolution et Biodiversité - Institute of Systematics, Evolution and Biodiversity). These harvests enrich the collection through the addition of specimens picked while on dry land or in an aqualung, as well as by assembling collections of tissue and DNA associated with the specimen collection.

The activity surrounding the collection is therefore primarily scientific. Indeed, the presence of so many types, the worldwide distribution of the specimens and their large quantities enable taxonomic, phylogenetic and biodiversity studies (diachronic and synchronic) to be carried out. These characteristics make it the most important tool of its kind in the world. The algae collection is also a historical collection in the sense that the preserved specimens, which are often accompanied by drawings and notes, can form a basis for research into the collectors’ networks, the evolution of naturalist practices and the history of the zones explored.