Francis Masson was the first official plant collector of the Royal Botanic Gardens, Kew. Between 1776 and 1779 he undertook extensive plant collecting on the Macaronesian archipelagos of Madeira, the Azores and the Canaries. This field trip marked a major milestone in the plant exploration of the region, with material collected by Masson resulting in the description of over 118 species by famous plant taxonomists or naturalists such as Linnaeus filius, William Aiton, Leopold von Buch, Nicolaus J. Jacquin, Charles-Louis L’Héritier and Johann H. F. Link. During Masson's visit to these islands, he sent letters accompanying three shipments of plant material to Linnaeus and Linnaeus filius. We believe that this was the only correspondence ever received from Macaronesia by the distinguished Swedish naturalists. In order to contribute to the worldwide celebration of the 300th anniversary of the birth of Linnaeus, we undertook an investigation into the nature and significance of these shipments. We found that this plant material was the basis for 37 descriptions provided by Linnaeus filius. Our study showed that a total of 21 and 61 herbarium specimens were sent to Linnaeus and Linnaeus filius, respectively. In addition, 53 accessions of seeds were sent to Linnaeus the younger. Identification of plant material was carried out after studying Masson's collections and the relevant taxonomic literature. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 393–428.