6 ANCIENT PLANTS 



CHAPTER II 



VARIOUS KINDS OF FOSSIL PLANTS 



Of the rocks which form the solid earth of to-day, 

 :a very large proportion have been built up from the 

 deposits at the bottom of ancient oceans and lakes. 

 The earth is very old, and in the course of its history 

 <lry land and sea, mountains and valleys have been 

 formed and again destroyed on the same spot, and it 

 is from the silt at the bottom of an ocean that the hills 

 of the future are built. 



The chief key we have to the processes that were 

 in operation in the past is the course of events passing 

 under our eyes to-day. Hence, if we would understand 

 the formation of the rocks in the ancient seas, we must 

 ;go to the shores of the modern ones and see what is 

 taking place there. One of the most noticeable char- 

 acters of a shore is the line of flotsam that is left by the 

 edge of the waves; here you may find all kinds of land 

 plants mixed with the sea shells and general rubbish, 

 plants that may have drifted far. Much of the debris 

 {outside towns) is brought down by the rivers, and may 

 be carried some distance out to sea; then part becomes 

 waterlogged and sinks, and part floats in to shore, per- 

 haps to be carried out again, or to be buried under the 

 coarse sand of the beach. When we examine sandstone 

 rock, or the finer grained stones which are hardened 

 mud, we find in them the remains of shells, sometimes 

 of bones, and also of plant leaves and stems, which in 

 their time had formed the flotsam of a shore. Indeed, 

 one may say that nearly every rock which has not been 

 formed in ancient volcanoes, or been altered by their 

 heat, carries in it some trace of plant or animal. These 

 remains are often very fragmentary and difficult to re- 

 cognize, but sometimes they are wellnigh as perfect as 

 dried specimens of living things. When they are recog- 



