ipart 2] ANNIVERSARY ADDRESS OE THE PRESIDENT. lxxix 



The Silurian Period was one of quiet sedimentation in seas 

 teeming with animal life. With a few exceptions Algse are prac- 

 tically the only plants i:>reserved, hut in some localities fragments 

 have been found which may well belong to some of the first 

 representatives of the vegetation of the land. 



During the vast cycles of time represented by the Lower 

 Palaeozoic systems, to borrow the words of Sir Archibald Geikie, 

 ' generations of sea-creatures came and went in long procession, 

 leaving their relics amidst the ooze of the bottom '. At last, it 

 would seem that we have vestiges of plants which grew above 

 the tides. One is tempted to regard these imperfectly-preserved 

 fragments with the same kind of feeling as that which is evoked 

 by the first flush of light at the end of a long, dark night. But, 

 before passing on to consider the oldest records of a terrestrial 

 vegetation, I propose briefly to consider a few of the genera of 

 Pre-Devonian fossils usually included in the plant-kingdom. 



The frequent association of microscopical tubules with oolitic 

 structure in rocks ranging in age from the -Cambrian to the 

 Cretaceous Period is a well-established fact. In his Presidential 

 Address to the Geological Section of the British Association in 

 1913, Prof. E. J. Garwood gave an admirable summary of the 

 available data. The unseptate tubes have been compared Avith 

 the sheaths surrounding some recent species of the widely-spread 

 blue-green algse, but August Rothpletz preferred to regard them 

 as cells of a somewhat higher alga allied to the Codiacese. We are 

 still unable to say what Girvanella is ; it may be an alga : it is 

 conceivably similar in nature to the sheaths surrounding existing 

 thread-like bacteria. Whether it deserves all the credit that it 

 has received as a rock-builder is doubtful : its association with 

 oolitic grains may be secondary, not primary. The genus is 

 recorded from Cambrian rocks of China, Australia, Sardinia, and 

 America ; from the Ordovician of the Old and New World, the 

 Silurian of Europe and Australia ; it occurs in abundance in 

 Carboniferous limestones as also in Jurassic rocks, and has recently 

 been discovered in the Albian Series of Angola. Whatever its 

 true nature, Girvanella represents a persistent type. 



The genus JEpiphyton, originally described by J. G. Bornemann 

 from Cambrian rocks in Sardinia, has been discovered in Siberia and, 

 more recently, by Dr. W. T. Gordon in a boulder dredged from the 



