GYMNOSPERMS 



319 



the same age, but gymnosperms did not become really abun- 

 dant until after the time of the greatest profusion of pterido- 

 phytes. In this next age gymnosperm trees became dominant, 

 and large numbers of fossil remains tell strange stories to 

 those who can understand them; stories of many kinds of 

 ancient seed plants, of giant tree trunks when gymnosperm 

 trees first reached high into the air as a result of the struggle 

 for light, and of seeds when the 

 seed habit was first developing. 



In those times gymnosperms 

 were almost everywhere. The 

 " big trees " and redwoods 

 extended to Greenland, and 

 cycads and other groups now 

 well-nigh extinct grew in pro- 

 fusion over very wide areas. 

 The Pine family was not so 

 abundant then as were other 

 gymnosperms, but became abun- 

 dant later and to-day is a fairly 

 successful group. This abun- 

 dance of pines and their rela- 

 tives in some regions may often 

 be explained by the fact that 

 in poor soil and under severe 

 climatic conditions they are 

 exposed to little competition 

 with other trees. 



These remnant forms of the formerly luxuriant gymnosperm 

 groups have undergone many changes, but here and there over 

 the earth they stand as still living evidences of the class of plants 

 that dominated before the highest class, the angiosperms, be- 

 came the leading plants of the earth. Changes in the climate and 

 in the physical conditions of the earth, and the struggle for ex- 

 istence, has doubtless often reduced or eliminated one group 

 of plants and made possible the dominance of another group. 



FIG. 264. A branch from the 

 " maidenhair tree " (Ginkgo) 



About one third natural size 



