38 LAND LIFE BEGINS 



described. It is useful to try to picture this early 

 earth on which a new act of the drama of life was 

 opening. There was little solid land. A warm ocean 

 rolled over the greater part of the surface of the globe, 

 and in it the story of life had so far proceeded. The 

 atmosphere was foul and thick, quite unsuitable for 

 such land animals as we know, and generally saturated 

 with moisture. The enormous quantities of carbon 

 and moisture in it let only a sombre light of the sun 

 pierce through; but, on the other hand, they pre- 

 vented the heat from being freely reflected back into 

 space, and an almost tropical climate existed all over 

 the earth. There was no winter season. Frost and 

 snow were unknown anywhere. 



The land now began to gain on the water. Ridges 

 of hill no doubt arose, but most of the new "dry" 

 land would be broad swamp and mud-flat. Upon 

 these shores life began to crawl from the overcrowded 

 ocean. Plants must have led the way, since animals 

 would need them for food. We know that the con- 

 ditions — steamy swamps and an atmosphere rich in 

 carbon — were good for such types of vegetation as 

 there were at the time, and as they became adapted 

 to land life, or swamp life, the}^ throve and evolved. 

 Low types of ferns and mosses appeared, and in the 

 rich, warm, low-lying earth they found a golden age. 

 As time went on they grew to gigantic proportions. 

 Most of them are now extinct, but the little "mare's 

 tail" which you find beside a stream to-day had a 



