The Pines 



p. 

 p. 

 p. 



Cones 3 to 6 cm. long; leaves 2.5 to 6 cm. long. 9. P. 



Cones 2.5 to 4 cm. long; leaves 2 to 4 cm. long. 10. P. 



Cone-scales armed with slender spines. 

 Spines of the cone-scales short. 



Cones ovoid; leaves in 3's, 6 to 10 cm. long. .:. 11. 



Cones nearly cylindric; leaves in 5's, 2 to 4 cm. long. 12. 



Spines of the cone-scales long and slender, leaves in 5's. 13. 



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

 a. Cones subtcrminal. 



Leaves in 5'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. 14. P. 



Leaves 1.2 to 1.8 dm. long; cones oval, 5 to 6 cm. long. 15. P. 



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. 17. P. 



Leaves 0.7 to 1.5 dm. long; cones 11 cm. long or less. 18. P. 

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



monophylla. 

 edulis. 



chihualmana. 



Baljouriana. 



aristata. 



Torreyava. 

 arizotiica. 



16. P. resinosa.-^ 



ponderosa. 

 scopulorum. 



contort a. - 

 Murrayana. 

 palustris. 



22. P. rigida.-m 

 scrotiua. 

 ecliinata. 



P. 



Leaves dark green, 2.5 to 5 cm. long. 19. P. 



Leaves yellow-green, 5 to 7.3 cm. long. 20. P. 



Cones long-conic; resin-ducts of leaves away from the surface. 21. P. 

 b. Cones lateral (or subterminal in /'. caribcca). 



1. Leaves in 3's, or sometimes in 2's in P. ecliinata 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. 23. P. 



Cones conic or conic-cylindric. 



Leaves 13 cm. long or less; cones less than 7 cm. long. 24. P. 

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

 Cone-scales with sharp recur\'ed spines; resin-ducts in 



leaf near the surface. 25. 



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

 leaf not near the surface. 26. 



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 cur\ed 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. 31. P. glabra. 



Teed a. 



caribwa. VvS"^^^ \ 



