now. from 
species end 
of African < 
Botanical Survey of Tropical Africa.-The conclusion of the 
fourth volume of the Flora <>/ Tropical Africa affords an oppor- 
tunity for briefly summarising the whole of its contents with 
regard t<» the progress which it marks in the botanical survey 
of tropical Africa. 
When, in 1891, it was decided to resume the preparation of the 
Flora of Tropical Africa, one volume was assigned to the orders 
Oleaceae to Pedal iaccac of Bentham and Hooker's "Genera 
Pl;inr;inmi." At that time the number of species of those 
orders recorded as occuring in tropical Africa might have been 
estimate.! at somewhat over 700. Volume III. contain, l.li'.l 
species. Allotting to volume IV. approximately the same number 
of species, there was therefore a margin for 4<>u additional species, 
corresponding to an increase of 60 per cent. But so extraordinary 
was the accession of new material during the progress of the 
preparation of volume IV.. (hat in the end the number ot specif 
of the orders reserved for it rose to 2,176*. double the ongina! 
estimate. That, of course, necessitated th- subdivision <i rh. 
volurm into two parts, each quailing in b an ordinary volume. 
The increase was very unequal in different orders— as will be 
seen from the list given below— varying in the larger orders (ot 
over 100 species) from slightly over 50 per cent, in So 
well over.'iOO ner cent, in A,>n-ojnarPar. and almost t i>0 per cent, 
in /. ,aniarfur. Tin significance of these figures * 
more re;,dilv be gr.oped when we consider that the increase trom 
813* species known before 1891 to 2,176 known at present means 
'!.. 
added; audit We assume fed the same p 
the case of the orders dealt with in the first three volumes of the 
Flora of Tru v , >' 1 /W^the,, orders would, t worked out at 
Present, fill , ™ %'S 
exaggerated view may be seen from the fact that ^ Tropiart 
ibered 11 and 23 species respectively, are, in recently 
published monographs, represented by 36 and 92 species respec- 
This phenomenal increase of our knowledge of the flora of 
Tropical Africa since 1891 has been due to several causes u urn 
collect ions of ver\ consid ruble extent which had oi 
and partially been studied have now been worked aj 
cally^ Lrter's West African, Schweinf ur h £ iBata > and 
as new countries were opened up or the establishment of botanical 
"^These figures includeTnT^eTof -P^^^^S^S 
spared ; but it probabfy does not exceed 70 or 80, so 
■ ■ i on which were known from toopioal au.c 
