COSMOS. 



together in the newly-discovered land." It is a matter of 

 much importance to geology to compare the present dis- 

 tribution of plants over the earth's surface with that exhibited 

 in the fossil floras of the primitive world. The temperate 

 zone of the southern hemisphere, which is so rich in seas and 

 islands, and where tropical forms blend so remarkably with 

 those of colder parts of the earth, presents, according to Dar- 

 win's beautiful and animated descriptions,* the most instruc- 

 tive 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. 



Cycadeae, 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 coniferae from the coal formations upwards. 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 cycadeae, 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 cycadeae of the Jura 

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

 more ancient tertiary formations they are quite subordinate to 

 the coniferae and palms. f 



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

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

 ancient cryptogamic land plants, some few palms, many coni- 

 fers having distinct annual rings, and foliaceous shrubs of a 

 more or less tropical character. In the middle tertiary 

 period we again find palms and cycadeae fully established, an'd 

 finally a great similarity with our existing flora, manifested 

 in the sudden and abundant occurrence of our pines and firs, 

 cupuliferae, maples, and poplars. The dicotyledonous stems 

 found in lignite are occasionally distinguished by colossal 



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

 Beagle, 1839, p. 271. 



t Goppert describes three other Cycadeae (species of Cycadites and 

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

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

 Focene period. Goppert, Fossile Cycadeen, 8. 61. 



$ [Medals of Creation, vol. i. ch. v. &c. Wonders of 

 ~cL i. pp. 278, 392.] Z>. 



