208 THE AMERICAN NATURALIST [Vol. XL VI 



of material for its further study." Ward. In the suc- 

 ceeding decades, even to the close of the century, the 

 students of paleobotany were mainly occupied in accumu- 

 lating data as regards distribution, both areal and 

 vertical, and the opening decades of the present century 

 find the subject a recognized, respected, coequal part of 

 the general field of paleontology. 



Paleobotany, together with all the other branches of 

 paleontology, admits of subdivision into two lines or fields 

 of study — the biological and the geological — depending 

 upon the prominence given to the one or the other of 

 these phases of the subject. The biological study is, of 

 course, concerned especially with the evolution of the 

 vegetable kingdom, that is, with the tracing of the lines 

 of descent through which the living flora has been devel- 

 oped. As this side of the question will be taken up by 

 other contributors to this discussion, it may be dismissed 

 from further consideration, as the geological aspect is 

 almost exclusively the phase of the subject to which the 

 present paper is devoted. 



In the first place it will be necessary to call attention 

 to the fact that the successful use of fossils of any kind 

 as stratigraphic marks is — or at least may be — entirely 

 independent of their correct biological interpretation. 

 To most botanists, and indeed to some paleobotanists, 

 this statement will doubtless come as a surprise, since 

 they have come to imagine that the impressions of plants, 

 the form in which they are most made use of in this con- 

 nection, are so indefinite, indistinct and unreliable that 

 they can not be allocated biologically with even reason- 

 able certainty, and hence are of little or no value. As a 

 matter of fact hardly anything could be further from the 

 truth, and it can be confidently stated that it makes not 

 the slightest difference to the stratigraphic geologist 

 whether the fossils upon which he most relies are named 

 at all, so long as the horizon whence they come is known 

 and they are clearly defined and capable of recognition 

 under any and all conditions. They might almost as well 



