Scientific Intelligence. — Geology. 191 



Equisetciy of palms, jE?/r«fiaVa, and Najadea. According to 

 the genus and species, tliey have a much closer resemblance to 

 the plants between the Tropics than to those of our zone ; and 

 what is particularly deserving of observation, the same genera 

 and species are found in the most remote regions where the plants 

 now in existence are entirely different. The external forms of 

 the greatest number of fossil trees are very similar to the ar- 

 borescent ferns found between the Tropics. In England, 

 the Netherlands, Germany, North America and Greenland, the 

 Lepidodendrci are met with abundantly in grey wacke, in sand- 

 stone of the coal formation, and in the slate-clay of the black coal 

 formations. Impressions of the genus Knorria appear in the 

 greywacke of Magdeburg, in the slate-clay of Saarbriichen, and 

 as perpendicular petrified trees in the province of Orenburg, on 

 the confines of Asia. We obtained Pecopteris lanceolata, a 

 fern, and Rotularia marsiliiefbUa, a Nqjadea, from the black bi- 

 tuminous coal of Swina in Bohemia, — of Wettin in Germany, — 

 and of Huntington in Pennsylvania. Ferns, scaly trees, and their 

 attendant calamites, are to be found wherever black bituminous 

 coal of the older formation is discovered. The species, however, 

 are frequently different, and they therefore follow, in their clima- 

 tic and geographical distribution, the same laws observed by the 

 plants of the present world, and according to the relations of a 

 higher and more uniform temperature, which must be supposed 

 to have existed at some former period. An affinity depending 

 entirely on the same laws is observed in the more recent vegeta- 

 tion of the quader-sandstone formation, and upwards, through 

 all the coal formations. The family of trees with scaly bark 

 has disappeared ; dicotyledonous trees and shrubs have sup- 

 planted the ferns, which now appear seldomer, and under diffe- 

 rent forms. Palms and cycadaea have increased. The leaves 

 as well as the fruit of dicotyledonous plants are like the genera 

 called willows, maples, nut-trees, which are found abundantly in 

 brown coal. These likewise make their appearance in England and 

 Germany, at Hoer in Schonen, and probably in Surturbrand 

 in Greenland ; at which places we may conclude the tempera- 

 ture was formerly more uniform. If the facts here briefly stated 

 are compared, the consequent conviction must be, that vegeta- 

 tion, in its climatic and geographical distribution, has been con- 



