This article explores the relationship between science and empire, through the prism of British botanical engagement with the South Atlantic in the late eighteenth and early nineteenth centuries. It investigates the logistics of plant exchanges, as information, expertise, and specimens followed the maritime contours of the British empire. The discussion traces the nascent network-building undertaken by officials, residents, and visitors on St Helena and at the Cape of Good Hope, and the exchange of plant specimens with London and, crucially, with other places around the empire. The article suggests that such activities offer perspectives on wider patterns of interaction with an area located at the crossroads of Britain’s maritime empire. In time, the region forged its own botanical networks and created alternative axes of exchange, association, and movement.

The presence of five shallow-water scleractinian species at Ascension Island is confirmed, i.e. Favia gravida, Madracis sp., Siderastrea radians, Polycyathus atlanticus and Rhizosmilia gerdae. The three former are zooxanthellate, the two latter azooxanthellate. A sixth species, Cladocora debilis (azooxanthellate), dredged from moderately deep water is also expected to occur in shallow water. Madracis sp. and P. atlanticus are new records for the island. A previous record of Astrangia solitaria at Ascension is now referred to as P. atlanticus. Favia gravida, S. radians and C. debilis are amphi-Atlantic. Rhizosmilia gerdae is currently known only from Ascension Island and the Western Atlantic. None of the species are endemic to Ascension Island. No member of the family Dendrophylliidae has as yet been found at Ascension, whereas that family is represented at its nearest neighbour, St Helena Island.