262 THE STOEY OF THE EARTH AND MAN. 



still a mystery. It has, however, been suggested that 

 this effect might result from the concurrence of such 

 astronomical conditions in connection with the eccen- 

 tricity of the earth's orbit as would give the greatest 

 amount of warmth in the Northern Hemisphere with 

 such distribution of land and water as would give the 

 least amount of cold northern land and the most 

 favourable arrangement of the warm surface currents 

 of the ocean.* 



Before leaving these Miocene plants, I must refer 

 to a paragraph which Dr. Heer has thought it neces- 

 sary to insert in his memoir on the Greenland flora, 

 and which curiously illustrates the feebleness of what 

 with some men passes for science. He says : " In 

 conclusion, I beg to offer a few remarks on the amount 

 of certainty in identification which the determination 

 of fossil plants is able to afford us. We know that 

 the flowers, fruits, and seeds are more important as 

 characteristics than the leaves. There are many 

 genera of which the leaves are variable, and conse- 

 quently would be likely to lead us astray if we trusted 

 in them alone. However, many characters of the 

 form and venation of leaves are well-known to be 

 characteristic of certain genera, and can therefore 

 afford us characters of great value for their recogni- 

 tion/' In a similar apologetic style he proceeds 

 through several sentences to plead the cause of his 

 Greenland leaves. That he should have to do so is 

 atrauge, unless indeed the botany kno fvn to those fo* 



* Croll and Lyell. 



