846 REPORT— 1903. 



Cretaceous sea flowed over the sites of Sinai and Ararat.' This Oretaceoiia epocli, 

 so recent geologically if measured by the standard of the antiquity of the ever- 

 lasting hills, has a remoteness beyond our power to appreciate. 



One interesting fact as regards the composition of the Jurassic Flora is the 

 absence of any plants that can reasonably be identified as Angiosperms. In the 

 "VVealden flora of England no vestige of au Angiosperm has been found ; this 

 statement holds good also as regards VVealden floras in most other regions of the 

 world. On the other hand, as soon as we ascend to strata of slightly more recent 

 age we are confronted with a new element in the vegetation, which with amazing 

 rapidity assumes the leading role. It is impossible to say with confidence at what 

 precise period of geological history the Angiosperms appeared. When the rocks 

 that now form the undulating country of the Weald were being accumulated as 

 river-borne sediments on the floor of an estuary, this crowning act in the drama 

 of plant evolution was probably being enacted. 



* Nothing,' wrote Darwin to Sir Joseph Hooker in J 881, 'is more extraordinary 

 in the history of the vegetable kingdom, as it seems to me, than the apparently 

 very sudden or abrupt development of the higher plants. I have sometimes 

 speculated whether there did not exist somewhere during long ages an extremely 

 isolated continent, perhaps near the South Pole.' We date the appearance of a 

 new product of evolution from the age of the strata in which it first occurs : but 

 this may well be a misleading criterion : all that we can say is that at a particular 

 period certain new types of organisms are brought within our ken. 



To quote Darwin again : ' We continually forget how large the world is, 

 compared with the area over which our geological formations have been carefully 

 examined ; we forget that groups of species may somewhere have long existed, 

 and have slowly multiplied, before they invaded the ancient archipelagoes of 

 Europe and the United States. We do not make due allowance for the intervals 

 of time which have elapsed between our consecutive formations, longer, per- 

 haps, in many cases than the time required for the accumulation of each format 

 tion.' 



On another occasion Darwin wrote to his friend Hooker : ' The rapid develop- 

 ment, as far as we can judge, of all the higher plants within recent geological 

 times is an abominable mystery.' Such evidence as we possess, meagre as it 

 admittedly is, shows that ' this overshadowing type of plant-life ' no sooner 

 appeared than it asserted itself with extraordinary vigour and created a revolu- 

 tion in the plant-world. Let us glance for a moment at the facts to be gleaned 

 from an examination of the records of this critical period in the history of vegeta- 

 tion. 



I have already pointed out that we have as yet recognised no Angiosperms in 

 the Wealden floras of England, Spitzbergen, Germany, France, Austria, Belgium, 

 Russia, and Japan ; but from plant-bearing rocks of Portugal, regarded as homo- 

 taxial with those which British geologists speak of as Wealden, the late Marquis 

 of Saporta named a fragment of a leaf Alismacites 2)rim(evus, a determination that, 

 while possibly correct, cannot be accepted as conclusive testimony. In Virginia 

 and Maryland there occurs a thick series of strata known as the Potomac forma- 

 tion from which a rich harvest of plant-remains has been obtained. Professor 

 Lester Ward has recently shown that under this title are included several floras, 

 some of which are undoubtedly homotaxial with the Wealden of Europe, while 

 others represent the vegetation of a later phase of the Cretaceous era. From the 

 older Potomac beds a few leaves have been assigned to Dicotyledons and referred 

 to such genera as Ficophyllum, Myrica, Proteapky Hum, a,nd others. Some of these 

 may well be small fronds of ferns with venation characters like those of the Elk's 

 Horn fern {Platyceriuin), while others, though presenting a close resemblance to 

 Dicotyledonous leaves, afibrd insufficient data lor accurate generic identification. 

 In dealing with fossil leaves of the dicotyledonous type, we must not forget that 

 the recent genus Gnetuni — a gymnosperm of the section Gnetales — possesses leaves 

 that may be said to be indistinguishable in form and venation from those of 

 certain Dicotyledons. Before the close of the Potomac period these few fragmen- 

 tary relics of possible Dicotyledons are replaced by a comparative abundance of 



