ANATOMICAL STRUCTURE AND CLIMATIC EVOLUTION 419 



epochs. The information derived from this source is not only 

 on the whole the most trustworthy, but it is likewise present in 

 sufficient quantity 

 from different geo- 

 logical periods and 

 diverse geographic 

 areas to justify 

 more or less com- 

 prehensive general 

 conclusions. In 

 the Paleozoic 

 trunks which are 

 supplied by the 

 geological forma- 

 tions of Southern 

 Canada the 

 organization of the 

 wood shows great 

 Uniformity, and FIG. 287. Transverse section of the wood of Cor- 



there are no daites from Prince Edward Island. 



modifications of 

 structure which 

 indicate any perio- 

 dicity in annual con- 

 ditions of growth. 

 The truth of this 

 statement is well 

 illustrated by the ac- 

 companying photo- 

 graph (Fig. 287) of 

 the wood of a cordai- 

 tean form from the 

 Permo- Carbonifer- 

 ous of Hampton, 

 Prince Edward 



FIG. 288. Transverse section of the wood of Cor- ^^ n &- The pres- 

 daites from the north of England. ence of clear zones 



