214 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLiSGOW, 



It follows, then, that no common dividing lines are to be 

 expected, and that, in those cases at least which certainly make 

 up 12 per cent., and may form 80 per cent., of the British Flora, 

 river- valleys exercise no influence whatever. So far, I have 

 simply been treating of the British Flora, but during my botanical 

 journeys I have myself seen many dividing lines of the floras in a 

 larger sense. In South Africa there are at least four ; in West 

 Africa there are two very distinct ones, the upland or Upper 

 Niger Flora seen at Falaba, and the Coast Flora ; in Egypt there 

 are distinctly three ; in Madagascar three ; in Central Africa, 

 from Mombassa to Uganda, and thence by Tanganyika to the 

 Zambesi, seven difierent floras, more distinct in each case than 

 the floras of Italy and Scotland.^ 



In every single case the dividing lines are indistinct; they 

 remind one of the very excellent description by Mr. Miller Christy 

 of the range of Primula elatior, Jacq., in Britain.^ 



The flora, as a whole, is defined by certain general climatic 

 considerations, usually very obvious if one takes the amount 

 and distribution in time of the rainfall, but in only one single 

 case did I feel that the line could be drawn on the ground. That 

 was in Egypt, where the boundary of the Nile overflow was 

 clearly marked by the vegetation. 



In all the other cases there is a debatable land ; the rainfall is 

 not the same every year, but varies yearly within pretty broad 

 limits, and, no doubt, is also slowly changing over a series of 

 years in one or the other direction. 



Let me take two examples from my own experience — one well 

 known, and one never, to my knowledge, published. Mr. Bolus 

 has thoroughly described the Cape Flora. ^ The characteristic 

 Clifibrtias, Ericas, Proteas, &c., of the Cape Peninsula are not 

 found in the Karoo, because the Karoo has no rain, and at a 

 certain season the Cape Peninsula has. Yet there is a broad 

 debatable land in which the two floras mingle, quite impossible 

 to mark definitely, and with, I think, a few endemic species not 

 found either in the Karoo or in the Cape Peninsula. The second 



^ I have not included special Alpine belts. 

 2 Journ. Linn. Soc, Vol. XXXIII., p. 172. 



^ Handbook to the Cape Colony. Also Trans, and Proc, Bat. Soc. Edin. 

 Paper read November 14th, 1889. 



