5 4- ORGANIC EVOLUTION" 



under some remote heading, find some allusion 

 to it. 



Such evidence as is afforded by the fossilised 

 remains of plants — those preserved by petrification 

 have been of chief value — teaches us most unequi- 

 vocally the truth of the doctrine of organic evolution. 

 In amazinsr measure — if we consider the conditions 

 under which the evidence has been preserved — 

 does the actual historical record coincide with that 

 hypothetical table of genealogy which the botanist 

 might amuse himself in reconstructing from the 

 facts of the vegetable life now extant. Arguing 

 from the known facts of comparative anatomy he 

 would regard it as probable, let us say, that the 

 ferns are older than the flowering-plants, the algae 

 or bacteria older than the ferns. And when the 

 proposition is put to the rocks, they affirm it by 

 yielding evidence of ferns, but none of flowering- 

 plants, in strata older than those which yield 

 fossilised remains of both ; and so forth. 



If we make an ideal section of the earth's crust, 

 we find that, above a certain level, there begin to 

 appear remains of living things. It is, of course, of 

 great interest in relation to the origin of life, to 

 determine the characters that differentiate the 

 strata above this level from those below it ; but here 

 we will simply accept the fact that, at a certain 

 level, there appear signs of past life. The many 

 strata above this level may conveniently be divided 

 into three successive lots, which are called primary, 

 secondary, and tertiary ; or palaeozoic, mesozoic, and 

 cainozoic, to indicate that they contain ancient, 

 intermediate, and recent animal remains. Lately we 



