202 SECTIONAL ADDRESSES. 



there are undoubted examples of structure which may be described as 

 more primitive than any we know in the world to-day, we note a surprising 

 resemblance in the general plan of construction between the inconceivably 

 ancient and the most modern members of the plant-kingdom. Attention has 

 been directed by many writers to the recently acquired knowledge of the 

 floras that have left well-preserved samples in rocks of the Devonian period : 

 we speak of Devonian plants as the oldest known relics of terrestrial 

 vegetation ; but we cannot believe that in them we have the first of a 

 succession of colonists which spread over the face of the earth. Whether 

 they are regarded as the modified descendants of more ancient types, 

 which evolved in the sea and subsequently accommodated themselves to 

 existence above the tides ; or whether we prefer to think of Devonian 

 plants as descendants of Silurian or still older progenitors, the fact remains 

 that their ancestry is shrouded in mystery. Stress has been laid on 

 certain morphological features presented by members of the older Devonian 

 floras ; on the other hand, we must remember that the best-known of these 

 extinct plants lived in swamps and under conditions that were favourable 

 to their preservation as fossils. We know only in part : our knowledge is 

 based largely on a particular kind of plant association, which from the 

 nature of its habitat escaped destruction during recurrent geological 

 convulsions ; and it is reasonable to assume that there were contemporary 

 associations occupying other situations of which we know nothing. Words 

 used by the late Prof. Bury in reference to the history of human societies 

 are applicable to geological history : — 



' All the epochs of the past are only a few of the front carriages, 

 and probably the least wonderful, in the van of an interminable 

 procession.' 



A few plants have been recorded from Devonian rocks in South Africa, 

 but the records so far obtained from beds below the Karroo system are 

 very disappointing. Further research may yield valuable results : it is 

 a laborious task to look for fossils in ground that is mostly barren, though 

 the search is worth making. It is almost entirely from Devonian rocks of 

 the northern hemisphere that our information has been gained : Australia 

 has furnished a few specimens, and a few fragmentary remains have been 

 described from the Falkland Islands. 



Leaving the Devonian period we pass to the Carboniferous and Permian 

 periods, and here there is much to discuss which has a special application 

 to South Africa. In the northern hemisphere the rocks of the Carboni- 

 ferous system tell a fairly clear story : during the first half of the period 

 comparatively deep seas spread over wide areas in North America and 

 Europe in which there slowly accumulated masses of calcareous material, 

 derived mainly from shells of marine organisms and the framework of 

 lime-secreting algae. 



At many localities abundant disjuncta membra of plants have been 

 found in sediments deposited in shallow water near the coast-lines, and in 

 volcanic ash flung from craters over forest-clad regions beyond the reach 

 of the sea. This Lower Carboniferous vegetation, though more varied 

 than that of the latter part of the Devonian period, was its direct derivative. 

 Identical genera and identical, or at least very closely allied, species have 

 been found in North Eastern Greenland, in Spitsbergen, in Europe and 



