VI PREFACE. 



collections were no longer available for study at Kew, and Professor 

 Oliver eventually abandoned the further prosecution of the work. He 

 retired from his official post in 1890. 



Meanwhile the publication of the first three volumes had considerably 

 stimulated botanical research in Africa. Sir John Kirk had become 

 Consul-General at Zanzibar, and lost no opportunity of encouraging 

 collectors. Sir H. H. Johnston, K.C.B., H.M. Commissioner in 

 British Central Africa, imitated his example in British Central Africa. 

 Much valuable work in Equatorial Africa was also done by the 

 missionaries of the Church Missionary Society. The Temperate flora dis- 

 covered on Kilimanjaro by the Rev. C. New, who was probably the 

 first human being to reach its snow-line, and the collections subsequently 

 made by Mr. Joseph Thomson on the mountains of East Equatorial 

 Africa confirmed the relationships of the high-level floras of Tropical 

 Africa with those of the northern hemisphere on the one hand and of 

 the Cape on the ^ other, which were first indicated by Mr. Mann's 

 collections on the Cameroons. These relationships raise theoretical 

 questions of the highest interest. The various Delimitation Commissions 

 which followed the partition of the continent each yielded botanical 

 results of more or less value. And the addition of new territories 

 to the Colonies on the West Coast stimulated the desire of their 

 Governments for an investigation of their vegetable products. 



The result was that an immense mass of material poured into Kew, 

 and, though individual collections were worked out in a series of scattered 

 papers, a general demand sprang up in foreign countries, as well as at 

 home, for a comprehensive work which would sum up the knowledge 

 which had been acquired, with no little expenditure of labour and even 

 of life, of the vegetation of Tropical Africa. 



The desire eventually found expression in the following letter : — 



"Foreign Office to Royal Gardens, Kew. 



"Foreign Office, March 21st, 1891. 



" Sir, — I am directed by the Marquis of Salisbury to state to you that 

 his attention has been called to the fact that three volumes only of 

 the ' Flora of Tropical Africa ' have as yet been published, and that 

 the want of a complete handbook describing known plants impedes 

 their study by Her Majesty's officers in the difierent parts of Africa 

 which are now being opened up to civilisation. 



"A knowledge of African botany is of great practical value, as was 

 proved by the discovery of Sir John Kirk, whilst employed as Her 

 Majesty's Agent at Zanzibar, of a plant previously unknown, which 

 now supplies annually £200,000 worth of india-rubber to the Zanzibar 

 market. So, too, on the West Coast of Africa, the trade consists 

 almost entirely of vegetable products some of which have only recently 

 been brought to light. 



" Lord Salisbury is of opinion that a proper knowledge of the flora of 

 Tropical Africa would do much to aid the development of the territories 



