PREFACE. VII 



in the specimens examined by the authors, and which in nature 

 are often departed from according to circumstances favourable or 

 unfavourable to luxuriance, in which the plant may be placed. It 

 may be observed, however, that relative proportions often hold 

 good, while absolute size may be widely different. Nor must 

 undue importance be attached to the more prominent and briefly 

 expressed characters made use of in the synoptical tables which 

 are given under each genus of two or more species. These are 

 intended to serve rather as guides in the determination of the 

 species than as absolute or final indications, and must always be 

 checked by a comparison of the specimen with the more detailed 

 description. 



In citing the several localities for each species, it has appeared 

 expedient to arrange them under six principal geographical regions 

 into which the enormous area embraced by this Flora has been 

 divided.* These are : — 



1. Upper Guinea, including under this term the Western 

 Coast region from the river Senegal on the north to Cape Lopez, 

 immediately south of the equator ; the interior drained by rivers 

 intermediate between these limits ; and the small islands of the 

 Gulf of Guinea, Fernando Po, Prince's Island, St. Thomas and 

 Annabon. 



2. North Central. The Sahara eastward to the countries 

 watered by the Nile and its tributaries, including also Bornu and 

 Haussa. 



3. Nile Land. The area drained by the Nile, extending some 

 three or four degrees south of the equator, so as to include the 

 plants collected by Captains Speke and Grant, after leaving the 

 watershed coastwards on their way from Zanzibar to the Victoria 

 Nyanza. 



4. Lower Guinea. Western tropical Africa, from Cape Lopez 

 southward to the tropic of Capricorn, including Congo, Angola, 

 Benguella, and Mossamedes. 



* To the citation of localities, the sign (!) is added whenever a specimen has 

 been actually seen by the author. An asterisk (*) is prefixed to those species 

 which are believed to have been introduced. 



