436 Darwin, and after Darwin. 



precarious, and this in so high a degree that any conclusions 

 raised on such premises are not entitled to be deemed for- 

 midable \ 



Turning now to plants, the principal and the ablest 

 opponent of the theory of evolution is here unquestionably 

 Mr. Carruthers 2 . The difficulties which he adduces may be 

 classified under three heads, as follows : 



i. There is no evidence of change in specific forms of 

 existing plants. Not only are the numerous species of 

 plants which have been found in Egyptian mummies in- 

 distinguishable from their successors of to-day ; but, what 

 is of far more importance, a large number of our own 

 indigenous plants grew in Great Britain during the glacial 

 period (including under this term the warm periods between 

 those of successive glaciations), and in no one case does it 

 appear that any modification of specific type has occurred. 

 This fact is particularly remarkable as regards leaves, 

 because on the one hand they are the organs of plants which 

 are most prone to vary, while on the other hand they are 

 likewise the organs which lend themselves most perfectly 

 to the process of fossilization, so that all details of their 

 structure can be minutely observed in the fossil state. Yet 

 the interval since the glacial period, although not a long one 

 geologically speaking, is certainly what may be called an 

 appreciable portion of time in the history of Dicotyledonous 

 plants since their first appearance in the Cretaceous epoch. 

 Again, if we extend this kind of enquiry so as to include the 

 world as a whole, a number of other species of plants dating 

 from the glacial epoch are found to tell the same story 

 notwithstanding that, in the opinion of Mr. Carruthers, they 

 must all have undergone many changes of environment 



1 See Lay Sermons, Lecture on Geological Reform. 



2 See especially the following Presidential addresses : Geol. Assoc. 

 Nov. 1876; Section D. Brit. Assoc., 1886; Lin. Soc., 1890. 



