298 



ANATOMY OF THE GYMNOSPERMS 



Ray tracheids sparingly interspersed, strongly 

 reticulated throughout. 



16. P. serotina. 



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

 2, per tracheid, becoming bordered in the summer 

 wood. 



Ray tracheids sparingly interspersed, strongly 

 reticulated throughout. 



15. P. rigida. 

 Bordered pits in i row. 



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

 2 or 3, per tracheid, but very variable. 



Ray tracheids often predominant, interspersed, 

 sparingly reticulated. 



19. P. glabra. 



Summer wood dense (sometimes open in P. tasda and P. 

 cubensis). 



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 (very rarely strongly) 

 reticulated throughout. 



39. P. Ucda. 



Ray tracheids high, very strongly reticulated 

 throughout. 



Ray cells apparently all of one 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. 

 Bordered pits in i row. 



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

 2 or 3, per tracheid, but very variable. 



Ray tracheids interspersed, often predominant, 

 sparingly reticulated. 



19. P. glabra. 

 Bordered pits in i row, or sometimes in pairs. 



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

 2-4, per tracheid. 



