PINUS 297 



Pits on the lateral walls of the ray cells 1-5 per tra- 

 cheid. 



Ray tracheids strongly reticulated throughout, 

 often predominant, and, when interspersed, 

 very low. 



14. P. clausa. 



Pits on the lateral walls of the ray cells 1-4 per tra- 

 cheid. 



Ray tracheids chiefly high, conspicuously pre- 

 dominant, and strongly reticulated throughout. 



20. P. echinata. 

 Bordered pits in I row, sometimes in pairs. 



Pits on the lateral walls of the ray cells 1-4 per 

 tracheid. 



Ray tracheids chiefly high, conspicuously pre- 

 dominant, and strongly reticulated throughout. 



20. P. echinata. 



Epithelium of the resin passages (transverse) distinctly in i or 

 more rows, nonresinous. 



Summer wood dense, rarely somewhat open. 

 Bordered pits in 1-2 rows. 



Pits on the lateral walls of the ray cells 1-6, chiefly 

 2-4, per tracheid. 



Ray tracheids sparingly (rarely strongly) retic- 

 ulated throughout. 



39. P. tasda. 



Ray tracheids high, very strongly reticulated 

 throughout. 



Ray cells apparently all of i kind, but 



differentiating slightly. 

 41. P. cubensis. 



Pits on the lateral walls of the ray cells 2-5, chiefly 

 4, per tracheid. 



Ray tracheids commonly predominant and inter- 

 spersed, very strongly reticulated throughout. 



40. P. palustris. 



Epithelium of the resin passages (transverse) distinctly in i or 

 more rows, resinous. 

 Summer wood open. 



Bordered pits in i row or sometimes in pairs. 



Pits on the lateral walls of the ray cells 1-4, rarely 5, 

 per tracheid. 



