4 STUDIES IN FOSSIL BOTANY 



no conclusions of botanical interest could possibly be 

 drawn. 



The purpose which we have in view necessitates a 

 botanical arrangement of our subject-matter, but it is 

 essential for us also to bear constantly in mind the 

 geological horizon of the remains with which we are 

 dealing. In botanical history dates are just as im- 

 portant as in human history. In the former, however, 

 absolute dates are unattainable, and only relative ages 

 come into question. 



The imperfection of the geological record is a 

 familiar subject, and I need not dwell upon it here. 

 We naturally find that vegetable remains are by no 

 means evenly distributed throughout the series of strata. 

 From some formations they are almost absent, while 

 in others they are relatively abundant. Thus, beginning 

 at the top, the Miocene is rich in such remains, especially 

 in Switzerland ; so also is the Oligocene, as shown in 

 the Isle of Wight, and the Eocene, to which the very 

 rich leaf-beds in the Isle of Mull probably belong. 

 All these Tertiary plants bear, as we should expect, 

 a general resemblance to families now living. 



Passing to the Secondary system, the Cretaceous 

 formation is of special interest, for the first well- 

 characterised Angiosperms make their appearance in 

 these rocks. The remains from the Lower Greensand, 

 however, are of a different type, and often have their 

 structure well preserved ; they include some of the most 

 remarkable of fossil forms. The Wealden, which some 

 geologists reckon with the Cretaceous, and some with the 

 Jurassic formation, yields abundant remains, with which 

 we have become better acquainted thro'ugh the work of 



