288 THE HISTORY OF 



they become continually more defined, so that lastly, in the 

 most recent formations, for instance in the upper Brown coal 

 they appear marked just as distinctly as in the trees now 

 living in the same localities. 



A mere sketch, and imperfect, as is my representation of 

 the successive vegetations of the earth, our knowledge of 

 these past times is likewise, on a higher scale, imperfect and 

 fragmentary. If it be considered, how many accidents 

 must coincide in order that organisms, only to a certain 

 extent capable of recognition, should be enclosed in moun- 

 tain masses in process of formation, what manifold destroy- 

 ing forces must have rendered their influence felt upon 

 the organisms preserved, during the hundreds of thousands 

 of years which lie between the first origin of vegetation 

 and the existing world, it will not be found surprising that 

 our knowledge is here, more than anywhere else, mere 

 patch-work; but we shall not be able to withhold our 

 admiration from the men whose untiring industry, whose 

 ingenious combinations, brought to light and gave so high 

 a degree of certainty to what we know of the ancient 

 history of the Vegetable World. The names of Sternberg, 

 Brongniart, Goppert and Unger, are especially to be 

 mentioned, who have won for themselves immortal credit in 

 the Knowledge of the Flora of the Ancient World. 



I have only given a sketch of what we know, of what 

 existed in the different epochs of the earth's endurance ; 

 yet the question of what we know not, of the how it was, 

 may appear to many to possess no less interest. Here, 

 then, we come almost wholly into the region of arbitrary 

 speculation, we can only here and there draw tottering 

 analogies to endow our pictures with a weak semblance of 

 probability ; and, as it naturally occurs that the views of 

 individual inquirers vary to infinity, it is ridiculous and 



