GYMNOSPERMJE. 



133 



destruction down to the present day, so that what remains is a mere fragment of 

 what once existed. 



It was during the interval that elapsed between the formation of the newest 

 Chalk now left in England and the oldest Eocene, that Dicotyledons were introduced, 

 if not actually evolutionised, and our existing Flora practically came into existence. 

 All the Upper-Cretaceous Eloras of Europe also flourished during this interval, but 

 we cannot say, with our imperfect record, exactly the order in which they came in, 

 and must be content to regard them, in a general way, as far newer than they appear to 

 be stratigraphically. Much of the American Cretaceous series should, perhaps, also be 

 placed somewhere in this interval, though many well qualified to judge regard it as 

 dating from an older period. Without this digression we could not have formed so 

 adequate an idea of the completeness of the break between the Eocene and the Cretaceous 

 period, nor realised that the so-called Cenomanian and Turonian Floras of Europe may 

 belong to epochs completely different from those represented by the same horizons in 

 Kent and Sussex. 



The break in the continuity of the history of the Coniferae here introduced corre- 

 sponds to that which actually occurs in nature in our area. It is not to be understood 

 that this is the only gap in their history, for there are many, but there are none of such 

 present importance (or that perhaps are less adequately realised), for it immediately 

 precedes that chapter in their development with which we are most immediately con- 

 cerned, and it is absolutely necessary, therefore, that its magnitude and duration should 

 be recognised, in order to appreciate the meaning of the great change in the character of 

 the F'lora, which we find to have taken place in the interval. 



We have already seen that several very anomalous genera of Coniferae occur in 

 company with Dicotyledons wherever Floras of late Cretaceous age are met with. The 

 Aix-la-Chapelle Flora w^as very rich in these, and contains many new to science, which 

 may now be open to study. The curious genera Inolejns, Cypariasideum, and Spheno- 

 lepidiim were mentioned at page 17 of this Memoir. Cunninghamites, a genus differing 

 considerably from Cminingliamia, characterises the Cretaceous of Saxony and Bohemia. 

 Geinitzia is another genus which has been found abundantly at Quedlinberg, also in the 

 environs of Dresden, and near Neustadt in Austria. Its cones are cylindrical and elon- 

 gated, formed of scales at right angles to the axis, with peltate or hexagonal heads marked 

 with deep and converging grooves, and sheltering three or four wingless seeds at their 

 base, while the foliage is dimorphic, being closely imbricated as well as looser like that of 

 Cryptomeria. Nor must we forget that many of the supposed Cretaceous Sequoia are 

 very imperfectly known, and may prove when examined, to be as anomalous as those of 

 Aix-la-Chapelle already mentioned. It thus appears that a large proportion of even the 

 latest of the Cretaceous Coniferae belonged to types which have since become 

 extinct. 



It is quite otherwise when we reach the Eocene. The British Eocene Coniferae bear, 



