PLATE VI 



Prunus virginiana (13a and 13b) 



(Same synopsis as for Prunus emarginata, page 16) 



Purshia tridentata (14a and 14b) 



Vessels present; vessels rounded in outline; vessels grade 

 into smaller sizes as the growing season progresses with- 

 out an abrupt change in size; vessels solitary, in pairs, or 

 in various aggregates; perforation plates simple; axial 

 parenchyma present although few in number, diffuse; rays 

 one or two cells in width (rarely three). 



