In one of his papers on Malaysian Orchids R. Schleehter (1911) expresses his surprise that the flora of Celebes, though promising so much from a phytogeographical point of view, is very little known in comparison with that of the Philippines and Java and even with that of Borneo. In 1926 E. D. Merrill repeated this assumption with little less emphasis, and it is, indeed, still holding good even nowadays. I am not able to tell the reason why Celebes has been so much neglected in this respect, though it has been given ample attention by zoogeographers. Yet, botanical exploration has been carried out ever since the French scientific world cruises of the “Astrolabe” (1828) and the “Astrolabe” and the “Zelee” (1839). The more important collections have been enumerated in the “Appendix” to the present paper and among these the most outstanding ones are those made by the Neth. – Indian Forestry Service and by such individual collectors as Forsten (1840, N), Zollinger (1847, SW and Salajar), Teysmann and De Vriese (1860, N), Teysmann (1877, SW and Salajar), Warburg (1888, SW), Koorders (1894—’95, N), P. and F. Sarasin (1893—’96 and 1902—’03, all parts), Elbert (1909, SE), Schleehter (1910, N), Van Vuuren (1912—’14, SW, C, SE), Docters van Leeuwen (1913, Salajar, etc.), Kaudern (1917—’20, SE, C, E, N), Bunnemeyer (1921, SW), Lam (1926, Talaud), Kjellberg (1929—’30, SW, SE), Eyma (1938, C, E) and Monod de Froideville (1937—’39, SW, C, SE).