Ixviii COMMENTARY ON THE INTRODUCTION AND APPENDIX. 
good for the species I have not attempted to ascertain, nor have I attempted the sepa- 
ration of the tropical genera of either world for the totals above given. 
I regard the tropical African Flora as a subdivision of that of the Old World, because 
I find no other essential difference between the Asiatic and African vegetations taken as 
wholes than the poverty of the latter, and because the peculiar botanical features of 
large tracts of Asia are repeated in Africa. Thus the Punjab, Scinde, and S. Persian 
Flora is largely represented all over north tropical Africa, extending to the Cape de 
Verde Islands; the notable absence in the Deccan peninsula of India of Cupulifere and 
the extreme rarity of Conifere are conspicuous characters of all tropical Africa; and the 
Indo-Malayan Flora has- its representatives in Madagascar, and measurably on the 
coasts of the African mainland. If any part of the tropical Old World could be sepa- 
rated as a primary region that should rank as a kingdom, it would be New Guinea. 
III. The three Southern temperate regions | (Extratropical America, Africa, and 
Australia).—I cannot accept the merging the South-African Flora into the tropical 
African. Of the six well-defined botanical provinces of South Africa so ably established 
and limited by Mr. Bolus, not one is represented anywhere in tropical Africa, where 
there is no region of heaths, of Composite, of Crassulaceew, of Campanulacee, of Prote- 
ace, and of Restiacese, and where such few representative species of these orders as do 
occur are either confined to mountain-regions or are isolated amongst the prevalent 
Indian types of vegetation. On the other hand, the genuinely tropical types of Africa 
are few and scattered in its south temperate regions, where the Anonacee, Menisper- 
macee, Guttiferee, Rubiacee, Acanthacee, &c. are hardly even represented, and only 
locally. It is true that Mr. Bolus designates the western seaboard of South Africa as 
the tropical region, mainly because a palm there extends to 33° 30! lat. south; but as 
in New Zealand, the Himalayas, and at Gibraltar palms enter the middle temperate 
zone, their presence does not necessarily imply a tropical heat; and as the plants of 
the so-called tropical South-African region require no greater heat than that of an 
English conservatory, I cannot regard them as typical of a tropical Flora. 
In the above sketch I have taken no account of exceptional Floras like those of 
St. Helena and the Sandwich Islands, whose relationships must be determined by a study 
of the flowering plants they contain. Nor have I taken into account theoretical con- 
siderations of any kind. | 
With regard to exact geographical limitations of any of these seven botanical areas, 
such are possible only where geographical features present insuperable obstacles to the 
further spread of the plants that characterize them. Where two are conterminous, there 
is always a neutral ground, often a very broad one, and this neutral ground may itself 
present a Flora which may be regarded as either tropical or temperate. 
