The 'Vegetable Substances' collection was formed by the physician and collector Sir Hans Sloane (1660-1753) between the 1680s and the 1750s. All sorts of people ranging from ship's captains in the Americas to surgeons in the East Indies sent natural material from around the world to London. Sometimes this involved a variety of means and intermediaries, and in other instances individuals, including aristocratic women in London and Royal Society Fellows across England, gave items directly to Sloane. When Sloane received these samples of botanical items, he had them sealed into small glass and wood boxes. He then numbered these items and described the sample in a three-volume manuscript catalogue. 12,523 items are listed in Sloane's hand in this catalogue with varying degrees of information relating to their identification, contributor, provenance and use. Today, the Natural History Museum in London holds Sloane's surviving catalogue and over 8000 of these 'Vegetable Substances' objects. Considering the collection as a whole, this thesis explores the role of the 'Vegetable Substances' in early eighteenth-century natural knowledge. Using data provided by the catalogue and Sloane's surviving correspondence at the British Library, this thesis explores what is in the 'Vegetable Substances' and identifies how Sloane formed the collection by surveying the connections he developed with people across the world and how he managed these different relationships. Drawing on these exchanges, this thesis also focuses on the uses of the 'Vegetable Substances' by examining its contents in particular eighteenth-century contexts including gardening spaces and medicine.