42 FOSSIL COAL PLANTS. 



exaggerated. I have carefully avoided the creation of 

 species from unique, imperfect or doubtful specimens, for 

 every one who is at all familiar with the subject, must be 

 aware how much the science of fossil botany has been 

 retarded by a neglect of this necessary caution, on the part 

 of those who have published figures and descriptions of 

 fossil plants. 



One principal reason why this catalogue contains so many 

 species different from those before found in this country, is 

 that most of the fossil plants collected in America have 

 been obtained from the upper part of the coal series, where 

 the flora is quite different from that of the base of the 

 ' formation. 



The identity of our coal plants with those of Europe is a 

 matter that will require much careful study; and their 

 coincidences and differences can only be satisfactorily 

 determined by a comparison of numerous specimens of the 

 plants of the two countries. Indeed, I am disposed to think 

 that there has been much hasty generalization on this 

 subject, and that when the matter shall be fully investi- 

 gated, it will be found that, while generically there is all 

 the coincidence claimed, specifically there will be, perhaps, 

 less correspondence than has been supposed — probably 

 not much greater than among living plants of the same 

 classes. 



Nearly one fourth of all the living ferns of Europe are 

 found in North America, and the proportion of the lower 

 cryptogamous plants, common to the two continents, is 

 probably somewhat greater. 



Among our fossil plants, there are almost none which 

 present a perfect identity with those of Europe. And the 

 range which may be allowed to a species is yet an open 

 question, and one which must be determined, before deduc- 

 tions from the geographical distribution of fossil plants will 

 be conclusive. '^ ^ 



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