I'RESIDEXJIAL ADDRESS SECTION B. 51 



one sees suck readily saleable products as sheets, rods, pipes, 

 wire, alloys, metallic pigments, etc., being put on the market 

 rather than concentrates, matte, or unrefined metal. jS'ot 

 only is this the case, but there is another important side to 

 the question. The economical/ treatment of many ores 

 demands cheap supplies of certain chemicals. Thus the 

 extraction of zinc, or copper may often be best eft'ected by 

 leacliiiig with sulphuric acid. In localities far from the present 

 centres of production this involves undertaking the manu- 

 facture on the spot, and it need hardly be said that this is 

 a big step towards further industrial developments. Such 

 instances coidd readily be multiijlied, but it suffices for my 

 present purpose to point out that under existing conditions 

 we can enter upon these commercial undertakings without 

 fear of being undersold by Europe or America — a sure 

 indication of the progress which is bound to follow in the) 

 near future from the utilisation of our abundant natural wealth 

 under intelligent technical direction. 



CAUSES LEADIXG TOWARD PROGRESSIVE 



EYOLUTIOX OF THE FLORA OF 



SOFTH AFRICA. 



By T. R. Sim, D.Sc, F.L.S. 



Presidential Address fn Seefinn (', delivered J nhj 16, 1920. 



Wherever one travels in South Africa changes are seen 

 to be going on in the vegetation and in the nature of the 

 veld, and the longer one lives in South Africa and observes 

 what is happening, the more evident does it become to him 

 that the actions of civilised man are usually either directly 

 or indirectly connected with these changes, and that these 

 actions are often self-centred and exigent to a degree which 

 is not permanently beneficial to the community, and which 

 tends toward further and more serious changes in the future, 

 on which the life of South Africa as a habitable region 

 depends. 



I refer not only to changes in the local floras, but also 

 to resultant changes in the climate as a whole, influenced, if 

 not brought about, by these flora changes. I am led to take 

 this subject because with time and travel I see more definitely 

 the course and cause of changes constantly taking place under 

 our eyes upon everything which comes under our cognisance — 

 changes usually regarded as natural changes, which, o7i 

 account of their insidious nature, often pass unnoticed, or, if 

 noticed, are considered either trivial and not worth attention, 

 or else unsurmountable and so beyond our powers, neither of 

 which opinions are exactly- correct. 



