226 



COKEFERALES 



[CH. 



Hollick as Pinus triphylla, etc. The anatomical features are as 

 follows: annual rings narrow, not clearly marked owing v to the 

 walls of the summer-tracheids being thinner than in recent speci( 

 of Pinus; xylem-parenchyma confined to the periphery of the 



FIG. 727. Pityoxylon Benstedi. Radial section showing the tracheal pitting, tr; 

 rt, ray-tracheids ; p, ray cells with large pits; a, typical Abietineous pitting 

 of end- walls of medullary-ray cells. (After Stopes.) 



resin-canals which occur in any part of the wood and are often 

 filled with tyloses. The tracheids have a single row of pits not 

 contiguous or flattened; the pits on the tangential walls are 

 confined to the summer-tracheids; both linear and fusiform 



