Nos. 451-452.] ANATOMY OF THE COXIFERALES. 



layer. Radially the canal 

 frequent 



s continuous, but with more or. less 

 Pseudotsuga and Larix. The epi- 

 of narrow, cylindrical and much pitted cells 

 \ length in the outer layers where they become 

 five to seven times longer than broad, and finally they merge 

 with the parenchyma tracheids which replace them. 



While the general composition of the resin passage in 

 Pseudotsuga, Larix and I 



cyst, 



the 



requ 



stnctions in the canal mdi- 

 cate a partial survival of 

 the cystic formation. We 

 must therefore regard these 

 structures and the three 

 genera to which they be- 

 long as forming a transi- 

 tion group between the 



. the 



one hand and the perfectly 

 organized resin passage of 

 Pinus, with its canal of uni- 

 form width, on the other. 



In the genus Pinus, the 

 resin passages show con- 

 siderable variation in detail, ^'J^^^. 

 but they all conform to the 

 same structural type (Fig. 49). 

 round, often very large, and in 1( 

 fectly continuous passage of uni 

 consists of large, but very variabl 

 to several rows. In the soft pin( 

 trie zone of uniform width, but in 



