292 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



sic and Cretaceous, and the fourth making up the Tertiary and 

 Quaternary or Cenozoic. He thus laid the foundations of the science 

 in a broad way and was the inspiration of numerous students who 

 grew to productivity under his tutelage and example. 



During the remainder of the nineteenth century a vast body of 

 literature was built up by an ever-increasing number of students, of 

 whom the most illustrious were H. R. Goeppert (1800-1884), of 

 Silesia; Franz Unger (1800-1870), of Styria; Oswald Heer (1809- 

 1883), of Switzerland; Gaston de Saporta (1823-1895), of France; 

 and C. von Ettingshausen (1826-1897), of Austria. In Britain 

 W. C. Williamson (1816-1895), following the pioneer work of 

 Witham (1833) and Binney (1868), succeeded in placing the ana- 

 tomical study of petrified plants of the Carboniferous on a solid 

 foundation, and this phase of activity is still assiduously cultivated 

 by a considerable number of contemporary British botanists, among 

 whom D. H. Scott unquestionably stands at the head. In France 

 the most active contributors in recent years have been Bernard 

 Renault (1836-1904) to the anatomical side and C. Rene Zeiller 

 (1847-1916) to all phases of the subject. Probably the most capable 

 of contemporary paleobotanists is A. G. Nathorst, of Stockholm. 



The pioneer workers in North America were J. W. Dawson 

 (1820-1899) in Canada and Leo Lesquereux (1806-1889) and J. S. 

 Newberry (1822-1892) in the United States. Unger, in his Genera 

 et Species Plantarum Fossilium, had essayed a complete manual of 

 the subject as early as 1850, but a sufficiently large body of facts 

 had not yet been accumulated to give his work lasting value, although 

 it was of immense importance at that time. This task was accom- 

 plished by TV. P. Schimper (1808-1880) in three volumes of text and 

 one of plates of the Traite de paleontologie vegetale (1869-1874). 

 A less usable work covering the same field in a different way was 

 the Paleophytologie, contributed by Schimper and Schenk to Zittell's 

 Handbuch der Paliiontologie, which was completed in 1890. More 

 recently, A. C. Seward has essayed to cover the field in a four- 

 volume work on fossil plants (1898-1918), in which little space is 

 devoted to other than the morphological aspects of the subject, and 

 in which the flowering plants are entirely omitted. 



METHODS OF PRESERVATION. 



Fossil plants have been preserved by two principal methods: 

 They either became waterlogged and were buried in sediment rang- 

 ing from mud to sand, or were infiltered by some mineral solution, 

 or were replaced molecularly by silicic acid, calcium carbonate, or 

 other mineral substance. The first method is called inclusion, and 

 the degree with which the details are preserved in the resulting im- 

 pression depends on the fineness of grain of the sediment. Very 



