PALAEONTOLOGY. 293 



tropical forms blend so remarkably with- those of colder parts 

 of the earth, presents, according to Darwin's beautiful and 

 animated descriptions,* the most instructive materials for the 

 study of the present and the past geography of plants. The 

 history of the primordial ages is, in the strict sense of the 

 word, a part of the history of plants. 



Cycadea3, which, from the number of their fossil species, must 

 have occupied a far more important part in the extinct than 

 in the present vegetable world, are associated with the nearly 

 allied Coniferse from the coal formations upward. They are 

 almost wholly absent in the epoch of the variegated sandstone 

 which contains Coniferae of rare and luxuriant structure ( Vol- 

 tizia, Haidingera, Albertia) ; the Cycadese, however, occur 

 most frequently in the keuper and lias strata, in which more 

 than twenty different forms appear. In the chalk, marine 

 plants and naiades predominate. The forests of Cycadea3 of 

 the Jura formations had, therefore, long disappeared, and even 

 ; ri the more ancient tertiary formations they are quite subor- 

 dinate to the Coniferae and palms. t 



The lignites, or beds of brown coalj which are present in 

 all divisions of the tertiary period, present, among the most 

 ancient cryptogam! ; land plants, some few palms, many Co- 

 niferse having distinct annual rings, and foliaceous shrubs of a 

 more or less tropical character. In the middle tertiary period 

 we ajjain find palms and Cycadea3 fully established, and final- 

 ly a great similarity with our existing flora, manifested in the 

 sudden and abundant occurrence of our pines and firs, Cupu- 

 liferaB, maples, and poplars. The dicotyledonous stems found 

 in lignite are occasionally distinguished by colossal size and 

 great age. In the trunk of a tree found at Bonn, Noggerath 

 counted 792 annual rings. In the north of France, at Yseux, 

 near Abbeville, oaks have been discovered in the turf moors 

 of the Somme which measured fourteen feet in diameter, a 

 thickness which is very remarkable in the Old Continent and 

 without the tropics. According to Goppert's excellent inves- 

 tigations, which, it is hoped, may soon be illustrated by plates, 

 it would appear that " all the amber of the Baltic comes from 



* Charles Darwin, Journal of the Voyaget of the Adventure and 

 Beagle, 1839, p. 271. 



t GSppert describes three other Cycade.-D (species of Cycadites and 

 Pterophyllam), found in the brown carboniferous schistose clay of Alt- 

 attel and Commotau, in Bohemia. They very probably belong to the 

 Eocene Period. Gfiippert, Fostile Cycadccn,*. fil. 



t [Merlfih of Creation, vol. i., ch. v., &c. Wonders of Geology, vol. i 

 p. 278, 392.} Tr. $ Bucldaud, Geology, p. r>09. 



