xni THE GEOLOGICAL EVIDENCES OF EVOLUTION 397 



the earliest geological times, will probably be many hundred 

 times greater than those now existing of which we have any 

 knowledge ; and hence the enormous gaps and chasms in the 

 geological record of extinct forms is not to be wondered at. 

 Yet, notwithstanding these chasms in our knowledge, if 

 evolution is true, there ought to have been, on the whole, 

 progression in all the chief types of life. The higher and more 

 specialised forms should have come into existence later than the 

 lower and more generalised forms ; and however fragmentary 

 the portions we possess of the whole tree of life upon the 

 earth, they ought to show us broadly that such a progressive 

 evolution has taken place. We have seen that in some special 

 groups, already referred to, such a progression is clearly 

 visible, and we will now cast a hasty glance over the entire 

 series of fossil forms, in order to see if a similar progression is 

 manifested by them as a whole. 



The Progressive Development of Plants. 



Ever since fossil plants have been collected and studied, the 

 broad fact has been apparent that "the early plants — those of 

 the Coal formation — were mainly cryptogamous, while in the 

 Tertiary deposits the higher flowering plants prevailed. In the 

 intermediate secondary epoch the gymnosperms — cycads and 

 coniferse — formed a prominent part of the vegetation, and as 

 these have usually been held to be a kind of transition form 

 between the flowerless and flowering plants, the geological 

 succession has always, broadly speaking, been in accordance 

 with the theory of evolution. Beyond this, however, the facts 

 were very puzzling. The highest cryptogams — ferns, lycopods, 

 and equisetaceas — appeared suddenly, and in immense profusion 

 in the Coal formation, at which period they attained a develop- 

 ment they have never since surpassed or even equalled; while 

 the highest plants — the dicotyledonous and monocotyledonous 

 angiosperms — which now form the bulk of the vegetation of 

 the world, and exhibit the most wonderful modifications of 

 form and structure, were almost unknown till the Tertiary 

 period, when they suddenly appeared in full development, and, 

 for the most part, under the same generic forms as now exist. 



During the latter half of the present century, however, 

 great additions have been made to our knowledge of fossil 



