324 Transactions of the South Africayi Philosophical Society. 



tion of the Northern Hemisphere. I am aware that Passarge, in his 

 book on the Kalahari (Passarge, 1904) points out how this desert 

 region shows many traces of a former pluvial period, which he 

 correlates with the Pleistocene glacial period of the Northern 

 Hemisphere (see also Penck, 1905, p. 7) ; but I am quite unable to 

 accept his conclusions on this point, nor do I think that he has 

 proved that the Kalahari and other parts of South Africa are drying 

 up. All we know is, that South Africa in all parts (and perhaps 

 less so in the South-West Coast Eegion than in the others) is 

 subject to extreme fluctuations, as regards seasonal and annual 

 rainfall. 



I had already come to the conclusion that our climate could not 

 have altered materially, at least since Upper Cretaceous times, when 

 I received Prof. Gregory's remarkable paper, '* Climatic Variations : 

 their Extent and Causes " (Mexico, 1906), which thoroughly con- 

 firms my view, the logical outcome of which would be that in the 

 Northern Hemisphere the variations in climate, culminating occa- 

 sionally in " ice-ages," w^ould only have been produced by local 

 causes. If it be accepted " that former climatic changes " (in the 

 Northern Hemisphere) " involve less extreme changes of tempera- 

 ture than have been generally assumed, and that we are not called 

 upon to explain former tropical forests in the Arctic lands, or fossil 

 coral reefs in the Arctic seas, or occasional universal refrigerations 

 of the earth, then the problem of climatic variations is greatly 

 simplified " (Gregory, p. 14). "■ There is no evidence to show that 

 the Antarctic continent has ever supported a Flora essentially 

 different from what we would expect, if it had always been under 

 conditions similar to those which exist now." The fossil Conifers 

 found may well be explained as being the remnants of drift-wood, 

 and an Antarctic origin of any elements of our Flora seems to be 

 completely ruled out of court, and " nothing known from the 

 Antarctic regions is against the assumption that the mean climate 

 of the world is fairly constant " (Gregory, p. 7). ** The evidence 

 of palaeontology proves that the climatic zones of the earth have 

 been concentric with the poles as far back as its records go " 

 (Gregory, p. 7). 



With reference to the Flora of the Karroo Eegion, Dr. Bolus says 

 (1905, p. 28) : " The strength of the Flora to maintain itself under 

 the different conditions of a desert-like environment is shown by its 

 ability to push outward in every dry valley of the neighbouring 

 regions. The only marked exception to its great strength to resist 

 foreign invaders is also a tribute to its age — long adaptation to the 

 severity of its environment. For the one plant which has success- 



