J. Slarkie Gardner — Development of Dicotyledons. 165 



quired, according to Heer, to admit of the growth of the Greenland 

 floras, for it was above 70° Fahr. in the South of England, lat. 50°, 

 and 50^ Fahr. in Greenland, lat. 70°, the distance, difference in tem- 

 perature, and difference between the floras being as nearly as possible 

 equivalent to that existing between Madeira and England at the 

 present day. 



When we reflect that the first dicotyledonous floras of any extent 

 to be described were from the Miocenes of Italy and of Germany, we 

 are no longer surprised at the immense relative importance that that 

 formation assumed in the eyes of subsequent workers. It is small 

 wonder that Heer was led by comparisons with these and with the 

 well-known Miocene formation of Oeningen, to class all the dicoty- 

 ledonous floras of Switzerland as Miocene. As each is in turn 

 farther and farther removed in age from the horizon of Oeningen, 

 it is seen to contain a decreasing proportion of true Miocene types. 

 Thus, of the floras belonging to the Aqnitanian stage, only six out of 34 

 species at Ralligen, 27 out of 193 species at Monod, and seven out of 

 47 at Paudeze, are common to Oeningen. Yet each in turn, as it came 

 to be incorporated in the Miocene, has furnished fresh standards for 

 comparison, each addition approaching more nearly to Eocene types, 

 and departing more widely from those of the Miocene. By including 

 the Swiss Aquitanian and Mayencian in the Miocene, and then in 

 comparing Eocene and Oligocene floras of other countries with them, 

 the latter would be shown to possess Miocene characters, for there 

 can be little doubt that the Aquitanian floras are really Eocene, and 

 the Mayencian are truly Oligocene. We thus get at the root of the 

 matter, and though I could not induce the lamented Prof. Heer to 

 understand the grounds of my contention, I have no doubt that had 

 he lived to investigate our magnificent and typical series of English 

 floras, he must have modified his views. The process of assimilating 

 floras with the Miocene became a habit with him, and was always 

 justified by percentages. He persistently ignored Eocene floras, and 

 it was only the stratigraphical and overwhelming paleeontological 

 evidence as to the position of the Dakota and other floras of 

 America that led him to admit the Cretaceous age of the older 

 dicotyledonous floras. 



It was Heer's privilege to describe the floras of Greenland, and 

 he called them Miocene. Had it fallen to Saporta's lot, he would 

 possibly have assigned to them a Lower Eocene age, on account of 

 the considerable number common to Gelinden, including the typical 

 M'Glintoclda, which had not then been found in any other formation. 

 A student of our Reading flora would have assigned them to that 

 age. The Greenland flora has in its turn served to identify the 

 Mull and the Antrim floras as Miocene, and must have absorbed the 

 Gelinden flora and the American floras, had stratigraphical evidence 

 not intervened and made this impossible. Not the least remarkable 

 fact about these determinations is, that wherever the stratigraphical 

 evidence is nil, as at Antrim, Mull, and Bovey, the floras are Miocene ; 

 but where there is stratigraphical evidence, we hear of few Miocene 

 floras to the west of Switzerland. 



