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 [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 Gamopetale. ‘This I have followed 
in Vol.IV. 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, det péper te AtBin xavdvy, At the 
commencement of our era Pliny, if with a whimsical explanation, recalls 
the “ vulgare Grecie 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 yo 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 1906 (pp. 239, 240) has brought out in a 
