PALEOBOTANY- — BEERY. 



295 



simpler organisms that outlasted the complex or gave origin to new 

 types. The more complex lost their power of adaptability to change 

 and readily succumbed when such changes in their environment 

 came. For example, it was not the complex arborescent lepidoden- 

 droids that gave rise to the modern club mosses, nor were the lofty 



Fig. 1 .—Diagram showing the relative duration of geologic time, the successive dominance of plant types, 

 and the progressive increase in complexity of floras. 



calamites the progenitors of the modern mares tails, but in each 

 case simpler forms saved the phylum from becoming extinct. Fern 

 synangia may have given rise to seeds by modification and peripheral 

 sterilization, but no seed has or ever will become modified into a 

 synangium. Thus evolution either of organs or organisms is non- 



