conifers. SILVA OF NORTH AMERICA. 15 



Cones subterminal. 



Leaves slender, dark green, in 3-leaved clusters, from 8 to 18 inches in length ; scales 

 of the branch-buds silvery white ; cones elongated-conical, from 6 to 10 inches long, 



their scales armed with short stout recurved spines 33. P. palustris. 



Cones lateral. 



Leaves stout, dark green, in 2 and 3-leaved clusters, from 8 to 12 inches in length ; 

 cones ovate or elongated-conical, from 3 to 6£ inches long, dark brown and lustrous, 

 their scales armed with short slender prickles 34. P. heterophylla. 



