PLATE XXV 



Rhamnus alnifolia (47a and 47b) 



Vessels present; vessels solitary, in pairs, or in various 

 aggregates; vessels grade into smaller sizes as the growing 

 season progresses without an abrupt change in size; vessels 

 arranged in diagonal and/or radial lines; vessels angular in 

 outline; perforation plates simple; axial parenchyma predomi- 

 nantly terminal rays one or two cells in width (rarely three). 



Rhamnus purshiana (48a, 48b, and 48c*) 



Vessels present; vessels solitary, in pairs, or in various 

 aggregates; vessels grade into smaller sizes as the growing 

 season progresses without an abrupt change in size; vessels 

 solitary or in occasional multiples of a few cells; vessels 

 angular in outline; perforation plates simple; axial paren- 

 chyma predominantly terminal rays; one or two cells in 

 width (rarely three). 



