VI PREFACE. 



works in the series of which it is a part in having an official and not a 

 personal character. In the preface to the seventh volume I have given 

 an account of the circumstances of its initiation and of those under 

 which at the instance of the Government its preparation was resumed. 



In view of what I have said, I can have no doubt that I am adopting 

 the course which is most expedient in the interest of the work in 

 resigning the task of its completion to the present Director of Kew. 



It has been the practice in the more recent works that have been 

 prepared at Kew to conform to the classification and sequence of orders 

 adopted in Bentham and Hooker's "Genera Plantarum." This was 

 accordingly done by Professor Oliver, F.R.S., in the first and second 

 volumes. In the third he appears to have preferred the continuous 

 numbering of the cohorts given by Sir Joseph Hooker in his translation 

 of "A General ' System of Botany" by Le Maout and Decaisne. 

 Bentham and Hooker, however, in the " Genera Plantarum " commence 

 a new numbering of the cohorts for Gamopetalce. This I have followed 

 in Vol. lY. The numerical sequence does not therefore follow on from 

 that of Professor Oliver, but as the actual sequence adopted by him is 

 that of the " Genera Plantarum " anyone who cares to do so can readily 

 correct Professor Oliver's numbers. Unfortunately, in Vol. V. a further 

 correction is necessary. By one of those clerical oversights which can 

 only be accounted for by the frailty of human nature, the numbering of 

 the cohorts does not conform to either work. Personales should be ix. 

 instead oF xxiv. and Lamiales x. instead of xxv. 



Although the Old World has always had before it the problem of 

 unknown Africa, it is singular how tardy has been its exploration 

 compared with that of the New. Yet it has been for no lack of curiosity. 

 In the fourth century B.C., and possibly earlier, the Greeks had a 

 proverb preserved by Aristotle, aii cpepd n M^vr) Kaivov. At the 

 commencement of our era Pliny, if with a whimsical explanation, recalls 

 the " vulgare GrsecisB dictum semper aliquid novi Africam adferre." 

 In our twentieth century the novelty descends on the bewildered 

 botanist in a continuous flood, and more than one generation will come 

 and go without seeing it exhausted. 



A quarter of a century separates the three volumes of the " Flora 

 of Tropical Africa " issued by Professor Oliver from the fourth edited 

 by myself. Nothing more was claimed for the former than that they 

 were a " repertory" of what was known of the vegetation of the time, 

 imperfect as that knowledge was. Dr. Stapf in a memorandum in 

 the "Kew Bulletin" for 1900 (pp. 239, 240) has brought out in a 



