3/4 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



hausen's application of leaf-nervation as a means of identifying 

 fossil leaves, since the course of the leading bundles sometimes 

 showed the greatest variability within smaller and larger groups, 

 sometimes on the contrary showed scarcely any differences. 

 The shapes of the leaves could, in his opinion, at the most 

 be used only as a specific feature of distinction. To these 

 inherent difficulties in systematic botany was added the fact 

 that in the case of the fossil types it was quite exceptional to 

 find leaves, flowers, and fruits embedded in the same localities 

 in such a way as to demonstrate their original association with 

 one another ; and the want of caution displayed by many 

 inquirers had created a mass of palaeophytological literature 

 which for scientific purposes was little more than useless ballast 

 to be discarded. 



Schenk fearlessly and patiently carried out the task of sifting 

 the valuable results from the worthless, and by his precise 

 and comprehensive knowledge of living forms he brought the 

 scattered information regarding extinct forms into line with the 

 most recent aspects of botanical science ; his classificatory 

 treatment of fossil floras is now adopted by the best 

 authorities. 



Schenk was a warm supporter of Darwin's theory of 

 descent. His remarks on the genealogical relationships of the 

 different fossil groups of plants and the modifications and 

 variations of the ancient floras are of unusual interest. No 

 less suggestive are his inferences regarding the climates of 

 former ages and the general character of the vegetation. 

 Schenk's views on such subjects frequently differ from those 

 of Ettingshausen and Heer. 



The Marquis of Saporta (1823-95), the head of a noble 

 family, devoted all his leisure to the study of botany, and in 

 1860 began to interest himself especially in fossil plants. His 

 writings are among the most valuable descriptions that have 

 been given of fossil floras. They deal largely with the rich 

 Tertiary floras of Southern France. He described the famous 

 flora in the gypsum beds of Aix, in the Lower Eocene travertine 

 deposits of Sezanne (1865), in the marls of Gelinden (1873), 

 and in the Pliocene deposits of Meximieux (1876). Saporta 

 was also the author of several successful popular works, 1 which 



1 The most widely circulated of Saporta's books are The World of Plants 

 before the Appearance of Man (Paris, 1881 and 1885) and The Pahzonto- 

 logical Origin of Trees (Paris, 1888). 



