CHAPTER XVII. — SUCCESSION OF VEGETABLE LIFE. 389 



CHAPTER XVII. 



SUCCESSION OF VEGETABLE LIFE. 

 Archaan Plants — Palceozoic Plants— Mesozoic Plants. 



Order of Appearance in Time. It has been elsewhere 

 stated, that probably the living beings that first appeared on the 

 earth, were simple, undifferentiated forms, neither distinctly 

 animal nor vegetable ; but of this we have no positive proof ; 

 the conclusion is based upon our knowledge of the laws of 

 evolution, deduced partly from our study of the phenomena of 

 life as we observe them at the present time, and partly from the 

 meager, though significant record of forms preserved in the rocks. 

 All the evidence points decidedly to the simplest of beginnings, 

 but the positive record of these beginnings has been effaced by 

 the changes wrought during the immense period that has since 

 elapsed. The earliest pages of plant history, like those of human 

 history, are blank. The first plants that have left a definite record 

 of themselves are not found in the oldest sedimentary rocks, but 

 in those of comparatively recent origin, and they are not the 

 simplest plants, but those which are well up the scale of 

 development. 



Archaean Plants. The lapse of time, during which the 

 Archaean or oldest series of stratified rocks were formed, is 

 probably greater than that of all subsequent geologic times put 

 together. The thickness of these rocks must be fully fifty thousand 

 feet. Yet, in all this series, there has not been found the fossil 

 remains of a single organism that is undeniably such. There 

 has, it is true, been discovered in the Archaean of Canada a 

 supposed fossil protozoan, called Eozoon Canadense, but its 

 fossil character has not yet been settled beyond question ; it may 

 be merely a mineral formation. But it would be in the highest 

 degree unreasonable to conclude from this that no life existed. 

 There is every reason to believe that, during the formation of 



