The Pines 



Cones 3 to 6 cm. long; leaves 2.5 to 6 cm. long. 

 Cones 2.5 to 4 cm. long; leaves 2 to 4 cm. long. 

 Cone-scales armed with slender spines. 

 Spines of the cone-scales short. 



Cones ovoid; leaves in 3's, 6 to 10 cm. long. 

 Cones nearly cylindric; leaves in 5's, 2 to 4 cm. long. 

 Spines of the cone-scales long and slender, leaves in 5's. 

 B. Leaf -sheaths persistent, embracing the leaves at the base. 



a. Cones subterminal. 



Leaves in s's (sometimes in 3's in No. 15); western trees. 

 Leaves 2.2 to 3.3 dm. long; cones ovoid, i to 1.5 dm. long. 

 Leaves 1.2 to 1.8 dm. long; cones oval, 5 to 6 cm. long. 

 Leaves in 2's or 3's. 



Cone-scales unarmed; eastern tree. 

 Cone-scales armed. 



Cones oval to oblong-oval; resin-ducts of the leaves near the 

 surface; western trees. 

 Spines of the cone-scales stout; cones 7 to 15 cm. long. 

 Leaves 1.3 to 4 dm. long; cones 7.5 to 15 cm. long. 

 Leaves 0.7 to i.j dm. long; cones 11 cm. long or less. 

 Spines of the cone-scales slender; cones oblique, 2 to 5 cm, 

 Leaves dark green, 2.5 to 5 cm. long. 

 Leaves yellow-green, 5 to 7.3 cm. long. 

 Cones long-conic; resin-ducts of leaves away from the surface. 



b. Cones lateral (or subterminal in P. carihcea). 



1. Leaves in 3's, or sometimes in 2's in P. echinata and P. caribcea. 



Eastern trees. 

 Cones ovoid, globose, or broader than long. 

 Leaves 12 cm. long or less; cone-scales with stiff prickles. 

 Leaves 15 to 20 cm. long; cone-scales with small slender 

 deciduous or obsolete prickles. 

 Cones conic or conic-cylindric. 

 Leaves 13 cm. long or less; cones less than 7 cm. long. 

 Leaves 15 to 30 cm. long; cones i to 2.5 dm. long. 

 Cone-scales with sharp recurved spines; resin-ducts in 



leaf near the surface. 

 Cone-scales with short slender spines; resin-ducts in 

 leaf not near the surface. 

 Western trees. 



Cone-scales with stout spines. 



Cones 1.5 to 3.5 dm. long; spines very stout. 

 Leaves drooping; cones 1.5 to 2.5 dm. long, their 



spines upright or curved outward. 

 Leaves erect; cones 2.5 to 3.5 dm. long, their spines 

 curved inward. 

 Cones 7 to 13 cm. long; spines triangular. 

 Cone-scales with minute incurved spines. 



2. Leaves all in 2's. 



Eastern trees. 

 Spines of the cone-scales short, deciduous, or obsolete. 

 Cones ovoid to globose, straight; southern tree. 



9. P. 

 10. P. 



11. P. 



12. P. 



Z4P- 

 15- P- 



tnonophylla. 

 edidis. 



chihuahuana. 



Baljouriana. 



arislata. 



Torreyana. 

 arizonica. 



16. P. resinosa. 



17. P. ponderosa. 



18. P. scoptUorum. 

 long. 



19. P. 



20. P. 



21. P. 



contorta. 



Murrayana. 



palusiris. 



31. p. glabra. 



