88 DUDLEY MEMORIAL VOLUME 



Sheaths deciduous; leaves with 1 -vascular bundle, in 5s (except No. 6, 7) ; 



wood light-colored and soft. 

 Cones cylindric; scales thin; wings elongated; leaves in 5s, serrulate. 



White Pines. 

 Leaves not sharp-pointed; resin ducts not surrounded by strengthening 



cells. 



Leaves grayish green, soft, recurved or drooping; branchlets glabrous. 

 Leaves 5-8 inches long, drooping; cones 6-10 inches long; scales 



abruptly pointed at apex. 1. P. excelsa. 



Leaves 2-4 (rarely 5) inches long; cones 2-4 inches long; scales 



rounded at apex. 2. P. Strobus. 



Leaves bluish green, stiff and erect; branchlets puberulent; cones 



4-11 inches long; scales pointed. 3. P. monticola. 



Leaves sharp-pointed and stiff, 2-4 inches long, dark bluish green; resin 

 ducts surrounded by strengthening cells; cones 12-20 inches long. 



4. P. Lambertiana. 

 Cones not cylindric; scales thickened; wings reduced to a ring; leaves not 



serrulate. Stone Pines. 



Leaves in 5s; cones 2 l / 2 -3 inches long. 5. P. Cembra. 



Leaves in 2s or 4s; cones 4-2 inches long. 



Leaves in 4s. 6. P. quadrifolia. 



Leaves in 2s. 7. P. edulis. 



Sheaths persistent; leaves with 2 vascular bundles, in 2s or 3s (except Tor- 



reyana) ; wood resinous. Pitch Pines. 



Leaves in 5s, about 10 inches long. 8. P. Torreyana. 



Leaves in 2s or 3s. 

 Leaves in 3s. 



Cones with the umbo ending in a stout, hooked projection ; leaves 8 or 



more inches long. 

 Leaves grayish green, drooping; cones chocolate-colored, ovate. 



9. P. Sabiniana. 

 Leaves dull green, spreading; cones light brown, cylindric-ovate. 



10. P. Coulteri. 



Cones with rounded or flattened apophysis ; umbo with or without a 



slender prickle. 



Umbo with a prominent prickle ; apophysis but little thickened. 

 Branchlets glaucous ; leaves bluish green. 



11. P. Jeffreyi. 

 Branchlets not glaucous; leaves bright yellowish green. 



12. P. ponder osa. 



