FOSSIL PLANTS 221 



have enabled investigators to do much more than 

 generalize. 



What is true in regard to the scale of animal life is 

 also apparent concerning plant-life. The fossil record 

 furnishes ample proof of development, in spite of the 

 fact that there must have existed in the past a wealth 

 of plant forms of which we have no fossil evidence. We 

 know that in certain geological periods there were 

 groups of plants which were conspicuous and important, 

 but are now extinct. We are sure that certain groups, 

 such as the Club-Mosses (Lycopods) and Horsetails 

 (Equisetums), were once dignified and dominant, and 

 that now their glory hath departed, for such as exist 

 to-day are small and inconspicuous in comparison with 

 their giant ancestors. We know, also, that now is the 

 " Age of Angiosperms," with the odds in favour of the 

 Dicotyledons ; that the Angiosperms have asserted their 

 supremacy over the Gymnosperms, which were dominant 

 in the geological " Middle Ages." Ferns have persisted 

 from very ancient times. Many forms that flourished 

 in remote ages are extinct, but they have been replaced 

 by new species, and the group as a whole is probably as 

 flourishing to-day as it ever was in the past. What is 

 particularly remarkable is that fossils representing very 

 remote times indicate groups of plants wonderfully well 

 advanced in their own peculiar lines. 



The geologist speaks of Primary and Secondary rocks. 

 The Primary rocks are all igneous, or fire-formed. The 

 original solid crust of the earth must have been made of 

 such, but the term " primary " is applied to all igneous 

 rocks, whether those originally formed, or such as have 

 through the ages been intruded into the crust, or have 



