562 Notices of Memoirs — 



harvest of plant-remains has been obtained. Professor Lester Ward 



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



some of which ax'e 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, Protecephyllum, and others. Some of these may 



well be small fronds of ferns with venation characters like those of 



the Elk's Horn fern (Platy cerium), while others, though presenting 



a close resemblance to Dicotyledonous leaves, afford insufficient data 



for accurate generic identification. In dealing with fossil leaves of the 



dicotyledonous type, we must not forget that the recent genus Gnetum 



— 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 fragmentary relics of possible Dicotyledons are replaced by 



a comparative abundance of specimens which must be accepted as 



undoubted Angiosperms. Previous to the discovery of the supposed 



Angiosperms in Wealden strata of Portugal and North America, the 



earliest record of an Angiosperm was represented by Heer's Populus 



primcBva from Northern Greenland. This name was applied to a 



fragmentary specimen which may be a true dicotyledonous leaf. In 



1897 Dr. White, of the Geological Survey of the United States, 



stated that additional examples of dicotyledonous leaves had been 



obtained during the visit of the Peary Arctic expedition to the 



well-known locality in Greenland where Heer's Populus primceva 



was discovered in the so-called Kome series. From strata known as 



the Atane beds, which rest on the Kome series, unmistakable 



Angiosperms have been collected in abundance. 



Another indication of the sudden increase in the number of 

 dicotyledons is furnished by the Dakota flora of the United States — 

 in age somewhat more recent than the older Potomac beds. In these 

 plant-beds it is stated that Angiosperms constitute two-thirds of the 

 vegetation. 



One of our most pressing needs is a thoroughly critical revision of 

 the late Cretaceous and earlier Tertiary floras, with the object both of 

 determining the systematic position of the older Angiosperms and 

 of mapping out with greater accuracy the geographical distribution 

 of the floras of the world in post- Wealden periods. This is a task 

 which is sometimes said to be impossible or hardly worth the 

 attempt ; the available evidence is indeed meagre, and much of it has 

 been treated with more respect than it deserves, but it is at least 

 a praiseworthy aim, not to say a duty, to take stock of our material 

 and to compile lists of plants that may bear the scrutiny of 

 experienced systematists. We are profoundly ignorant of tbe means 

 by which Nature produced this new creation; we can only emphasise 

 the fact that in the early days of the Cretaceous era a new type was 

 evolved which no sooner appeared than it swept all before it, and by 

 its overmastering superiority converted the past into the present. 



In conclusion, I would ui'ge the importance of taking stock of our 

 accumulated facts, and of so recording our observations that they 



