320 Science of Plant Life 



so minute and delicate that we cannot hope to find their fossil 

 remains. Yet we know that plants of some kind did exist 

 on the earth at that time, for the fossils of corals and of shell 

 animals are abundant in these rocks, and without plants to 

 manufacture food for them, life would have been impossible 

 for these animals. In rocks that were formed later than 

 these first fossil-bearing strata, remains of fernHke plants are 

 found. Later there were seed-bearing fernlike plants and 

 several groups of plants intermediate between the ferns and 

 modern gymnosperms. Still later, gymnosperms resembling 

 in many ways our" coniferous trees became prominent, and 

 then came Angiosperms with very simple flowers of the wind- 

 pollinated type. Finally, Angiosperms with conspicuous 

 insect-pollinated flowers appeared. There is reason to be- 

 lieve that the first seed plants and the first flowering plants 

 were woody shrubs and trees, and that the flowering herbs 

 came last. 



The meaning of the record. The fossil record of plants 

 reaches many millions of years into the past, and it shows 

 that changes in plants came about only very slowly. The 

 plants of each geological period resembled in some respects 

 those of the previous period ; in each period certain new 

 characters were added to the old ones, or they replaced the 

 old ones. To reproduction by spores was added reproduction 

 by seeds. The first seeds were exposed on the sides of foliage 

 leaves ; later came seeds borne on scales arranged in cones ; 

 and finally came seeds inclosed in pistils. 



Leaves and stems also show progressive changes in form 

 and structure. Although the fossil record is very fragmen- 

 tary, being made up of chance imprints and petrified remains, 

 it is possible in some instances to discover when a group of 



