After my retirement Mr. R. E. Massey was appointed, in 1912, Sudan Government Botanist, and I had the good fortune of securing his co- operation in bringing out a more complete Catalogue of the Flowering Plants of the Sudan. Mr. Massey, by his presence on the spot, and by his technical knowledge, has been able to give to the present Catalogue a greater completeness and finish than I should have been capable of unaided; he was also able to get further assistance from other persons in the Sudan. He particularly and gratefully acknowledges the help he received from Mrs. Crowfoot, wife of Mr. J. W. Crowfoot, Director of Education, in a variety of ways, such as collections of plants, Hadendowa and other vernacular names, and drawings and paintings of plants. A number of Dinka and Shilluk names were also given by Mr. H. C. Jackson, of the Sudan Civil Service, and Nuer names by the late Major Stigand. A collection of plants of the Burun country, with their vernacular names, was received from Dr. Kamar, of the Egyptian Army, a further collection by Mr. Sillitoe, superintendent of Gardens, Khartoum, from the Lado District, and one from Admiral Lynes, C.B., C.M.G., in Darfur, mostly in the region of the range of mountains, called Jebel Marra, which attains an elevation of over 10,000 ft., and bears a flora quite distinct from all other parts of the Sudan. The Catalogue was at first compiled without any descriptive matter, but Mr. R. Hewison, Director of Agriculture and Forests, Sudan Government, speaking on behalf of that Government, which is defraying the costs of printing this book, expressed an opinion that it would be more useful to officials in the Sudan if short descriptions were added. In order, therefore, to supply these as quickly as possible we depended very largely on descriptions in the Flora of Tropical Africa, which we shortened considerably. My wife and I worked this out as far as and including the Cyperaceæ, and Mr. Massey undertook to do the grasses, part only of which have as yet appeared in the Flora. He desires to acknowledge the aid received from Mr. C. E. Hubbard in the preparation of the key to the Grasses. Mr. J. Hutchinson kindly helped us with plants in the Kew Herbarium which have not been described in the Flora. But a further acknowledgment is due to Mr. Hutchinson. He has regrouped the Natural Orders according to the system described in his recent book, _The Families of Flowering Plants, I. Dicotyledons_,[2] and has also furnished a key to the Classification, thus bringing this book into line with all the African Regional Floras which are to be taken in hand. He has also consented to look over the proofs. Our most cordial thanks are due for his help. My wife has been constantly associated with me in my share of the work from the time when we collected material in the Sudan until now, and deserves also to earn her share of whatever credit may be given for this work.