A. F. G. Kerr (1877—1942) worked in Siam between 1902 and 1932, originally as a doctor, later as government botanist. He made large botanical collections in Siam and surveyed the whole of that country. Our knowledge of the flora of Siam is mainly based on his collections (now completely represented at Kew and in the British Museum), which formed the materials for the Florae Siamensis Enumeratio. A sketch of his life and career is given, also a bibliography, including special publications devoted to Kerr or to his material and details about his collections; by means of an Itinerary the date can be found of any Kerr number as well as the locality with approximate longitude and latitude, and by means of a list originally prepared by Kerr himself and here posthumously published, for each geographic name the province and the region of Siam where it is situated. Several persons were inspired by Kerr to make botanical collections themselves, notably Anuwat, Bourke-Borrowes, Mrs. Collins, Garrett, F. H. W. Kerr, Lakshnakara, Marcan, Noe, Put, Rabil, Rock, Eryl Smith, H. M. Smith, Vanpruk, Winit, Yuang. Some information about these persons and their collections has been added.