BORDERED PITS 



This is undoubtedly a primitive character, and in the one case 



cited it possesses some value for the purpose of specific differ- 

 entiation, but in general terms the occurrence of bordered pits 



in such positions is of so sporadic a nature 



as to give this feature no well-defined value, 



either for taxonomic or phylogenetic purposes. 



It may, nevertheless, be stated with respect 



to the pits on the tangential walls of the tra- 



cheids in general, that in their distribution 



they distinctly conform to the law governing 



similar structures on the radial walls. 



Reference to Cordaites acadianum shows 



that in the multiseriate pits of the hexagonal 



form these structures always preserve the 



spiral arrange- 

 ment character- 

 istic of the 

 structures from 



which they FIG. 12. SEQUOIA GI- 

 were derived GANTEA. Radial 



section showing the 

 bordered pits on 

 the tangential walls 

 of the spring wood. 



/ 



x 280 



FIG. 13. SEQUOIA GIGANTEA. Tan- 

 gential section showing bordered 

 pits in the tangential walls of the 

 spring wood, x 280 



(plates 3-6), 

 and this con- 

 formity also ex- 

 tends to the 



direction of the spirals which gen- 

 erally ascend from left to right. 

 The general law in this respect has 

 already been formulated so fully 

 by De Bary (13, 163) as to make it 

 unnecessary at this time to enter 

 upon its consideration more in 

 detail, beyond a reference to one 



or two special features and some apparently exceptional cases. 

 While the spiral arrangement is always typical in such genera as 

 Cordaites, Dammara, Araucaria, etc., it is not obvious in those 

 cases where the pits are strictly one-seriate and often remote 



