PINUS 301 



Ray tracheids predominant, sparingly retic- 

 ulated. 



33. P. scopulorum. 

 Bordered pits in i row, sometimes in pairs. 



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

 per tracheid. 



Ray tracheids more or less reticulated in the 

 summer wood, often interspersed. 



25. P. Murrayana. 



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

 3-4, per tracheid. 



Ray tracheids strongly predominant, strongly 

 dentate, and more or less reticulated through- 

 out. 



31. P. Jeffrey!. 



Pits on the lateral walls of the ray cells (i) 1-4; 

 and (2) 1-3, chiefly 2, per tracheid. 



Ray tracheids often predominant, reticulated 

 throughout. 



27. P. Coulteri. 

 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. tseda. 



Ray tracheids high, very strongly reticulated 

 throughout. 



41. P. cubensis. 



Summer wood dense, more rarely somewhat open. 

 Bordered pits in i row. 



Pits on the lateral walls of the ray cells (i) 1-4; 

 and (2) 2-4, chiefly 4, per tracheid. 

 Ray tracheids predomi nant, sparingly reticulated. 



33. P. scopulorum. 

 Bordered pits in I row, sometimes in pairs. 



Pits on the lateral walls of the ray cells (1)1-4 ; ar >d 

 (2) 1-3, chiefly 2, per tracheid, the two forms of 

 cells clearly defined. 



Ray tracheids reticulated in the summer wood, 

 predominant in the low rays of which they 

 often compose the entire structure. 

 36. P. muricata. 



