42 FORESTS AND MANKIND 



Back in those earlier days of tree life, the continent of North 

 America looked quite different and possessed a more temper- 

 ate climate. Rainfall was more abundant. The weather was 

 warmer, more uniform in temperature and there was a total 

 absence of frost. The Rocky Mountains had not yet been 

 formed and the whole continent was low and heavily wooded 

 from coast to coast. At that time there were no regions of tree- 

 less areas like our Great Plains, neither was there any abrupt 

 difference between the forests of the east and the west. Greater 

 uniformity existed both in the climate and topography and 

 conditions were everywhere favorable to tree life. The cold, 

 inhospitable wastes of the Arctic in those days were warm 

 tree-covered areas where even the heat-loving fig and palm 

 found favorable conditions and conifers flourished and grew 

 over all the land. It was an ideal world for them. They were 

 the highest form of plant life in it. 



Time passed. Many thousands of years. The outlines of 

 North America had meanwhile been changing. The Gulf of 

 Mexico and the Arctic Ocean mingled their waters by means 

 of a great inland sea that cut through the continent. Gradually 

 this inland sea subsided and a large variety of tropical plants 

 invaded the Gulf region from the south. 



Then came a great and important change. Following the 

 conifers arose a class of trees that are commonly called broad- 

 leaf trees because their leaves are not needle-like, such as the 

 leaves of the spruce and the pine, but broad and flat like the 

 maple and hickory. These broad-leaf trees were of a later type. 

 They were more complex in their nature than the cone bearers 

 and better able to survive and establish themselves and their 

 descendants. They were the "moderns" of the plant world and 



